Moving U.S. Forces: Options for Strategic Mobility Section 7 of 12
February 1997

Chapter Five

Evaluating Lift Requirements
and Capabilities

With fewer combat units stationed abroad today, the United States needs strategic mobility forces to project its military might. But at a time when all types of federal funding are tightly constrained, it is important to revisit the issues of how much strategic mobility is enough and what mix of lift forces best suits the needs of the United States.

Since the end of the Persian Gulf War, the Office of the Joint Chiefs of Staff has coordinated two analyses of the U.S. military's strategic lift needs: the 1992 Mobility Requirements Study, and the 1995 Mobility Requirements Study Bottom-Up Review Update (MRS BURU). Rather than looking at a broad range of scenarios in which the United States might need to move its forces, both analyses focused on a few scenarios that military planners believe will place the greatest demands on strategic mobility. However, because determining future lift requirements involves making a host of assumptions, the results of those and similar analyses are bound to be contentious.

Problems in Identifying Lift Requirements

The authors of the MRS BURU evaluated the military benefits of delivering combat forces more quickly by judging whether earlier arrivals would reduce the risk that U.S. forces would face. But the uncertainties in any analysis of mobility requirements are enormous-- so large that some mobility experts believe that analysis alone cannot provide a final answer about how much lift is enough.(1)

The Uncertainties of Planning for Deployments

The Department of Defense's requirements for mobility forces are open to question because they hinge on a large number of assumptions about how major deployments will take place. First, there is the nature of future conflicts: which aggressors might the United States face? How would they prosecute an attack? How much warning might leaders have? Will the United States have support from host nations or coalition partners? Second, there is uncertainty about which U.S. forces would be sent to the conflict, and whether they are adequately trained and ready to deploy. Finally, there are uncertainties about whether military and commercial transportation would be available when needed and would perform as expected. Those uncertainties are so fundamental that there will always be room for debate over how much lift is enough.(2)

Despite the uncertainties, of course, defense officials must still decide how to allocate resources for lift. Because the future is unclear, military planners would probably prefer a larger number of mobility forces to handle any sort of contingency. But acquiring enough mobility forces to address all uncertainties would almost certainly be unaffordable.

Airlift requirements set by DoD planners during the Cold War provide an example. During the early 1980s, DoD set a goal of purchasing 66 million ton-miles per day of airlift capacity--more than twice the level that existed at the time. The Congress invested a considerable amount of money to achieve that goal, including funds to buy C-5Bs and KC-10s and to develop the C-17. But that substantial investment left DoD far short of its goal with around 50 MTM/D of airlift capacity. And even the 66 MTM/D goal was not nearly large enough to address what defense officials thought they would need for a conflict with the Soviet Union; that level was lowered because of fiscal realities.(3)

Balancing Risk and Cost Versus Setting Absolute Requirements

The uncertainties surrounding plans for strategic mobility are probably greater today than during the Cold War, when defense officials could focus on planning for a major conflict against the Soviet Union in Central Europe. But mobility planners faced similar problems even then. As a senior analyst who led research on mobility requirements for the Office of the Secretary of Defense during the 1980s commented:

There's a lovely quote from Harold Brown that says "There's no such thing as a defense requirement." There is nothing about which you can say, "With this I shall surely succeed, and without this I shall surely fail. . . ." I keep trying to strike the lexicon of requirements out of people anyway--it's too arguable. . . . You can't prove that you have to get there on that schedule.(4)

Ultimately, policymakers must decide how much the United States is willing to pay to lower the risks associated with deploying forces abroad. But some might argue that defense planners occasionally focus on absolute requirements--the minimum number of forces that they believe will meet DoD's military needs--with-out fully weighing the relative risks and costs of alternative levels.

An example of that might be found in the Administration's 1995 recommendation to buy a total of 120 C-17s for DoD's airlift fleet. Defense officials based that decision in part on the findings of an Air Force study that compared the costs and capabilities of such a purchase with those of three airlift planes: the C-17, the C-5D, and the C-33 (a military version of the Boeing 747-400 freighter). As explained in Chapter 2, that analysis found that certain combinations of C-17s and alternative planes could deliver nearly as much cargo to major regional conflicts as an airlift fleet with 120 C-17s, even if airfields were congested. Yet in their decision, DoD officials emphasized those alternatives that precisely matched the capabilities of 120 C-17s rather than options that were somewhat less capable but much less costly.

Supporters of the decision would counter that defense officials did evaluate the alternatives thoroughly. In their opinion, those options simply gave up too much military capability.

Mismatch Between the Assumptions of War Fighters and Mobility Planners

One factor that highlights the difficulty of setting numerical requirements for strategic mobility is the difference in approaches between officials who plan for combat and those who plan for mobility. A recent DoD task force characterized the approach of war fighters as "just-in-case" planning, whereas DoD's mobility planners have tended to use "best-case" assessments of how much U.S. lift forces could deliver.(5)

War Fighters' Incentive to Minimize Risk. In a conflict, military troops are the people who face the consequences of risk most directly. Since the price of failure is so high, military commanders try to minimize the amount of risk that their personnel may face on the battlefield. One way to do that is to require enough strategic mobility assets so the United States could deliver overwhelming force very quickly.(6)

But, some defense analysts contend, transportation assets are always likely to be scarcer than regional military commanders would like. One reason is the organizational structure DoD uses to prepare for war. Specifically, because the responsibilities for minimizing risk and purchasing forces are separate, those military officials who plan for conflicts tend to treat transportation as though it were costless.(7)

DoD's organizational structure includes five U.S. regional commands that plan and prepare for military operations in different geographical areas of responsibility--roughly, Europe, East Asia and the Pacific, the Persian Gulf region, the Southern Hemisphere, and North America. Those commands are responsible for planning what types of forces they would need for conflict, setting priorities for the order in which the forces would be needed, and deciding when the forces would have to arrive.

During a war, the regional commander in chief would be responsible for conducting combat operations using forces from all of the military services. (The U.S. Atlantic Command would provide the regional commander with the forces he needs, and the U.S. Transportation Command, which plans and coordinates transportation between theaters, would move the troops to the appropriate theater of operations.) That organizational structure was designed to strengthen joint military planning and limit the influence of any one service. However, the military services and the Office of the Secretary of Defense control funding for new weapon systems and mobility forces--not the regional commanders. Thus, although regional commanders are responsible for minimizing the risk to U.S. forces, they do not directly face the cost of equipping troops or purchasing the means to transport them.

Regional commanders can voice their opinions about which mobility forces to buy through the recommendations of the Joint Requirements Oversight Council, an organization designed specifically to give officials in charge of combat more input into DoD's acquisition decisions. The council's recommendations frequently hold considerable sway. Regional commanders can also influence key decisions such as whether sets of equipment should be prepositioned on land in their geographic area (thereby falling under their organizational control) or on ships that, during peacetime, are under the purview of the military services.

Optimistic Assumptions by Mobility Planners. Whereas regional commanders have an incentive to want large numbers of forces for war, mobility planners tend to use assumptions about how much strategic lift forces can deliver that, on balance, are probably optimistic. In the MRS BURU, for example, mobility planners assumed that U.S. lift forces would operate in clear weather and would not face such hindrances as naval mines or surface-to-air missiles.

DoD's plan to deploy an effective defense to distant regions is based on many technical assumptions that affect the tempo of airlift and sealift operations. Those assumptions include the amount of warning of an attack, early decisionmaking to begin deployments, quick call-up of reserve personnel, timely access to commercial planes and ships, the availability of airfields and ports en route and in the theater of operations, and the amount of time that would separate the two conflicts (see Appendix C for more details about DoD's assumptions).

No one knows for sure how optimistic those assumptions are. But comparing what DoD expects to airlift to two major regional conflicts with what it was able to deliver to the Persian Gulf War offers some insight. According to DoD's estimates, in order to hold risk of mission failure to a moderate level, U.S. military and civil planes would need to supply about 60 percent to 70 percent more cargo (by weight) during the first two to three weeks of the second of two major regional contingencies than the United States was able to deliver during the first month of Operation Desert Shield. That estimate was for one of the most demanding scenarios outlined by military planners: sustaining a major conflict in Korea while delivering equipment for the halting phase of a second conflict in the Persian Gulf.

Is that swifter pace achievable? Some factors have changed that might allow the United States to airlift cargo more quickly. For example, today DoD has some of the more capable C-17 aircraft on hand; none were in its inventory during the Persian Gulf War. However, most of the expected improvement in airlift operations from what DoD experienced in the Persian Gulf War follows from assumptions about quick availability of commercial planes from the Civil Reserve Air Fleet, early call-up of reserve aircrews, and access to staging bases within the theater of operations.

Using the same assumptions as in the MRS BURU, DoD estimates that the United States might deliver an average of about 5,000 tons per day to an initial contingency in Korea over the first 30 days of deliveries, and about 5,000 tons per day over the first 15 days of deliveries to the second of two nearly simultaneous conflicts (see Figure 10). By comparison, the United States was able to move an average of only about 1,700 tons per day during the first month of Operation Desert Shield and just over 3,600 tons per day during the peak month of January 1991. Obviously, DoD is counting on much more efficient airlift deliveries in the future.

One difference defense planners are assuming is an earlier call-up of the Civil Reserve Air Fleet. During the Gulf War, DoD activated Stage I of CRAF 10 days after the start of deployments. But it did not mobilize Stage II until five months later, and it never called up Stage III. For the MRS BURU, mobility planners assumed that DoD would have access to Stage II planes much earlier in the first of two conflicts, and if a second contingency erupted, decisionmakers would activate Stage III.

Calling up Stage II sooner could significantly boost airlift deliveries. During the Gulf War, CRAF cargo deliveries jumped by an average of about 650 tons per day when Stage II was activated.(8) Over a two- to three-week period, that would have added 9,100 to 13,650 tons of cargo deliveries. In recent years, the Air Force

Figure 10.
Estimated Daily Airlift Deliveries to Two Major Regional Conflicts Versus Actual Deliveries in the Persian Gulf War

SOURCE: Congressional Budget Office based on data from the Department of Defense and John Lund, Ruth Berg, and Corinne Replogle, An Assessment of Strategic Airlift Operational Efficiency, R-4269/4-AF (Santa Monica, Calif.: RAND, 1993).

a. Results for two major regional conflicts assume an airlift fleet with 49 million ton-miles per day of theoretical capacity. For those estimates, the lefthand bar (showing the first 30 days) represents deliveries to an initial conflict in Korea; the righthand bar shows the first 15 days of deliveries to a second conflict in the Persian Gulf plus sustainment deliveries to Korea.

b. The peak month for airlift deliveries during Operations Desert Shield and Desert Storm was January 1991.

has encouraged airlines to place more of their planes in Stages I and II. Based on current CRAF enrollment, calling up Stage II would provide 76 more passenger aircraft and 57 more freighters beyond the amount already in Stage I, which could add considerably to delivery capability.

But those gains make a difference only if DoD has access to them earlier. And based on DoD's experience during the Persian Gulf War, some officials believe it is optimistic to assume that the United States would activate Stage II more quickly. In the opinion of some military and civilian defense analysts, many of DoD's other assumptions about timing--including the amount of warning, quick decisionmaking, and early call-up of reservists--are also optimistic. If so, DoD might take longer than its estimated two or three weeks to move enough forces to halt an enemy attack.

Some analysts might conclude from such uncertainties that DoD needs to invest its resources in the types of strategic mobility forces that arrive first at a conflict--that is, more airlift planes and prepositioned sets of equipment. However, others might argue that if halting an enemy invasion would take longer than two or three weeks, the military would ultimately need more heavy forces for its counterattack. Under those circumstances, DoD might do well to emphasize more prepo-sitioning and surge sealift in its deployment strategy rather than airlift.

Mobility Planning by Consensus

Planning for strategic mobility is an activity that is notoriously less glamorous in the eyes of military personnel than, say, planning tactical air operations or naval surface combat. Part of its status reflects the fact that airlift and sealift crews often provide transportation for Army troops rather than supporting their own military service. As a result, some defense analysts argue, airlift and sealift have until recently been "orphans" within the Air Force and Navy budgets: their advocates have tended to lose institutional battles for funding to missions with higher prestige.(9)

That perception was one impetus behind the Goldwater-Nichols Reorganization Act of 1986, which strengthened the role of joint military planning over the interests of individual services.(10) The Office of the Joint Chiefs of Staff was a major beneficiary of those efforts. In terms of strategic mobility, it has overall responsibility for coordinating the military's position on how much DoD will need. The Defense Department's Director for Program Analysis and Evaluation also plays an important role in evaluating which mobility forces best serve U.S. interests as a whole. In turn, the acquisition authorities within each military service and the Office of the Secretary of Defense weigh the recommendations of those organizations when developing their annual budget requests.

However, no single DoD office is responsible for both analyzing mobility forces and deciding how to spend resources. Recently, one method for coordinating the views of the various organizations who play a role in lift has been to conduct a major study of mobility requirements every few years. Those analyses involved the Joint Chiefs of Staff, the military services, the Office of the Secretary of Defense, the U.S. Transportation Command, unified regional commands, and other key organizations. Their primary goal was to look at trade-offs among modes of lift and make decisions about how to allocate resources. But a senior mobility researcher has characterized that decisionmaking process as follows:

In effect, DoD mobility planning proceeds by a committee process, with all the well-recognized advantages and drawbacks of such processes. Study projects, like committees, draw diverse organizations together and focus their attention on important questions. But there is a price. Committees tend toward consensus decisions that provide something for all participants.(11)

The most recent of those studies, the MRS BURU, recommended buying airlift planes and sealift ships to modernize U.S. mobility forces. But although those investments account for the vast majority of lift spending, some analysts contend that they contribute relatively little to addressing the major problem that the Joint Chiefs observed after the Persian Gulf War: how to reduce the risk faced by those U.S. forces who arrive at a conflict first.(12) DoD has addressed that risk by increasing the amount of equipment prepositioned in or near the Persian Gulf--a step that costs comparatively little.

The Importance of Smaller Investments

Recent studies of mobility requirements devote most of their attention to whether DoD should purchase major platforms. But larger numbers of planes, ships, and prepositioned stocks do not by themselves guarantee that future deployments will proceed more swiftly. Other, smaller investments can be equally important for major deployments.

DoD is already investing in facilities, equipment, and training that will help move troops from their peacetime bases to U.S. ports more quickly. For example, the Army has purchased railcars, improved railways, upgraded piers, and started constructing a facility on the West Coast to load ammunition into containers. Those measures have begun to address past problems that could slow troop movements within the United States.

But according to a recent DoD study, mobility planners need to continue focusing attention on alleviating bottlenecks that are likely to crop up at air and seaports both in the United States and in distant theaters of operation.(13) During the Persian Gulf War, for example, both airports and seaports in Saudi Arabia developed backlogs because there were too few trucks, heavy-equipment transports, pallets, elevator loaders, and the like to move the cargo forward.(14) Such bottlenecks are particularly troublesome because they can pose an attractive target for an enemy attack.(15) Thus, it is important to make those smaller investments that help move cargo within a theater and, in the event of a conflict, to make sure that units who operate seaports and airfields are among the first to arrive.

Other investments can have large payoffs as well. For example, having up-to-date intelligence about the characteristics of ports and airfields worldwide is vital. Knowing the capabilities of regional groups that might hinder U.S. mobility operations through small measures, such as naval mines, or more unconventional threats, such as chemical or biological attack, is obviously important as well.

Improving the information systems that DoD uses to command and control strategic lift is another critical way of smoothing mobility operations. During the Gulf War, for example, the electronic management system that theater commanders used to sort out and communicate their priorities for deployment became grid-locked.(16) Some of the system's users were simply unfamiliar with it; others found it so cumbersome that they circumvented it by sending messages for airlift missions. As regional commanders changed deployment schedules at the start of the conflict, several airlift planes were sent before units were ready to deploy, or were the wrong type of plane for the cargo load.

That problem was compounded by DoD's poor means of tracking which cargo loads and passengers were already en route to the war. Without that information, military leaders reordered deliveries of equipment and supplies, thus placing even greater demands on the mobility system.(17) Similarly, containers of materials were not always labeled, and a backlog grew as port operators opened many of them to verify their contents.

DoD has begun modernizing those information systems, making them easier to use. For example, the military has put bar codes on much of its equipment and containers to keep better track of them while in transit. Nevertheless, experts still believe that DoD's systems for managing information are relatively primitive by commercial standards.(18) More modern command and control systems would allow military commanders to adjust their deployment plans more quickly as tactical conditions changed.

DoD's Most Recent Requirements for Strategic Mobility Forces

Not long after the Office of the Joint Chiefs of Staff released its Mobility Requirements Study in 1992, the Pentagon completed the Bottom-Up Review, a comprehensive plan for future U.S. force structure. Subsequently, the Joint Chiefs updated their mobility study to follow the Bottom-Up Review's planning scenarios: fighting major regional conflicts on the Korean Peninsula and in the Persian Gulf. The result was the Mobility Requirements Study Bottom-Up Review Update.

The MRS BURU had a dual focus. On the one hand, the analysis used computer simulations of combat and deployments to estimate the number of planes, sealift ships, and prepositioning sites that DoD would need to deliver military forces within a specific time-line. On the other hand, its authors were warned that the plan for mobility forces resulting from the study would have to be affordable.(19) Thus, the MRS BURU tried to quantify how much risk U.S. forces might face while keeping an eye both on military objectives and on cost.

The authors of the review conducted simulations for four scenarios set in 2001--a single major regional contingency on the Korean Peninsula, one in the Persian Gulf, a conflict in Korea followed shortly by another in the Persian Gulf, and the same two conflicts but in the reverse order. The study concluded that two of those scenarios imposed the heaviest demands on U.S. mobility forces: a single conflict in the Persian Gulf, and two conflicts in which the Korean one began first.

In the case of a single regional conflict in the Persian Gulf, the MRS BURU concluded that the U.S. military would face a shortfall in the amount of lift needed to deliver enough forces to blunt an assault and keep warfighting risk at an acceptable (moderate) level. The study suggested that DoD resolve the shortfall either by purchasing additional airlift planes or by prepositioning another 280,000 square feet of cargo on ships closer to the region. That amount of cargo is equivalent to the capacity of one large, medium-speed roll-on/roll-off ship or two smaller roll-on/roll-off ships from the Ready Reserve Force. The total volume of cargo that DoD would need to transport to such a conflict is classified, but according to press reports, some defense officials believe that shortfall is small enough to fall within the margin of error of the models used to estimate lift requirements.(20)

Requirements for Prepositioning Afloat

The MRS BURU suggested that the Army preposition more combat-support and combat-service-support equipment on board ships to make up for the shortfall that would otherwise exist in a single major regional contingency. Specifically, the study recommended transferring one LMSR or two smaller ROROs to a prepositioning role from the fleet that would be used to surge equipment from the United States. DoD officials have not yet decided whether to follow that recommendation.

For a scenario in which the United States deployed forces to fight two conflicts, the MRS BURU's authors identified a fundamental problem related to the Army's heavy-brigade equipment prepositioned afloat in the Indian Ocean. That equipment is important for stopping an enemy assault quickly. But if it was used for a contingency in Korea, it would be unavailable for a second conflict in the Persian Gulf. The study recommended that, unless DoD prepositions more equipment or plans to withhold the Army's afloat prepositioning to use in a second conflict, it should plan to regenerate the prepositioning package. That is, after unloading equipment at the first conflict, the prepositioning ships would steam to the United States and take on a second set of equipment for the next conflict.

Requirements for Airlift

The MRS BURU recommended that DoD procure enough airlift planes to provide between 49.4 and 51.8 million ton-miles per day of theoretical airlift capacity. Rather than specifying a single requirement, the study set that range depending on how much more equipment military planners are able to preposition. If defense of-ficials can add 280,000 square feet to prepositioned stocks, 49.4 MTM/D might provide enough capability to complete deliveries for the halting phases of two major conflicts with an acceptable level of risk. However, if DoD cannot preposition more forces or if the Army's afloat prepositioning is not held in reserve for a conflict in the Persian Gulf, the study's authors believe more airlift is advisable.

The Administration's decision to purchase 120 C-17s would provide DoD with the 49.4 MTM/D of theoretical airlift capacity recommended by the analysis. To meet the higher level, the Air Force would need to procure a total of 140 C-17s or equivalent capacity with other airlift planes (after retiring all C-141s from service).

Following the MRS BURU, the Army conducted further analysis of what additional equipment it might preposition. Based on that work, DoD raised the requirement for theoretical airlift capacity to 49.7 MTM/D, making up the slight increase with deliveries by the Civil Reserve Air Fleet.

Requirements for Sealift

The MRS BURU concluded that the Navy should continue taking steps to fill the sealift requirements that were identified in the 1992 Mobility Requirements Study. That analysis called for purchasing 19 LMSRs, some of which would be used to preposition equipment, and establishing a fleet of 36 smaller ROROs for the Ready Reserve Force. Once those purchases were completed, the study's authors wrote, a number of older breakbulk ships could be retired from the RRF.

The MRS BURU also concluded that DoD could rely on commercial shipping to transport sustainment supplies in a timely manner. The analysis estimated that DoD would need to contract with shipping companies for 6,000 to 6,500 20-foot-equivalent containers per week to carry cargo, plus 13 to 16 containerships or a limited number of breakbulk ships to deliver ammunition under dedicated charter agreements.

Criteria for Evaluating Strategic Lift Options

Because of the uncertainties in forecasting mobility requirements, it is hard for policymakers to know how much lift the United States needs for the future and how it should be apportioned among airlift, sealift, and pre-positioning. Ultimately, that judgment is probably a subjective one, based on what decisionmakers believe is a reasonable balance between cost and capabilities. The rest of this chapter lays out criteria that the Congress may want to use in evaluating the Administration's plan for investing in strategic mobility and the alternative plans presented in Chapter 6.


Given the degree of competition for federal resources today, the cost of purchasing and operating mobility forces over the next several decades is obviously an important criterion. Because airlift is more expensive than sealift or prepositioning, an investment strategy that includes larger numbers of cargo planes will tend to cost considerably more.

The distribution of mobility costs among the military services may also be of interest to the Congress. For example, an investment approach that included more prepositioned sets of Army equipment and fewer airlift purchases would tend to raise annual costs for the Army and lower procurement spending in the Air Force's budget. That information may be of interest if, for example, one believes there are higher priorities within the Air Force's budget than buying cargo planes.

Cargo Deliveries to Major Regional Conflicts

Unless the Administration changes its approach to defense planning as a result of the Quadrennial Defense Review, the most demanding scenario for mobility is likely to remain two major regional conflicts that occur at nearly the same time. According to the MRS BURU, the greatest challenge to U.S. strategic mobility would come from a scenario in which a major conflict broke out on the Korean Peninsula followed shortly by another in the Persian Gulf region. Thus, it is important to consider how quickly alternative sets of mobility forces would deliver cargo in such a scenario.

Deliveries During the Halting Phase. Sealift ships require at least three weeks to load, steam from the United States to regions as far away as the Persian Gulf, and then unload their equipment. But under DoD's assumptions about how major conflicts would take place, the first U.S. forces would need to arrive within two to three weeks to halt an enemy assault.

If DoD's assumptions about timing are plausible, that halting phase would place the greatest demands on the fastest modes of transportation--airlift and preposi-tioning. The halting phase of a second conflict that overlapped an initial war would be especially arduous: DoD might need to deliver heavy units to the Persian Gulf and, at the same time, continue moving cargo to sustain operations in Korea. Thus, when comparing alternative plans for mobility forces, one important indicator is the amount of equipment and supplies that each could deliver two to three weeks after the start of deployments to the Persian Gulf.

Another important measure of capability is the amount of outsize cargo that different mixes of mobility forces could deliver to regional conflicts. According to DoD officials, the Korean scenario is the one in which airlift planes would need to fly into the most highly congested airfields. Thus, another key indicator of capability is the amount of outsize cargo that alternative sets of mobility forces could transport to the Korean Peninsula during the first two to three weeks of deployments.

Flexibility to Handle Changes in Deployment Schedules. In the fall of 1989, General Norman Schwartzkopf, then commander in chief of U.S. Central Command, began revising military plans in the event of an Iraqi attack on Kuwait or Saudi Arabia.(21) (Central Command is the regional command responsible for U.S. operations in the Persian Gulf.) However, Central Command had not completed its detailed schedule for deploying forces when its planning was overtaken by events. As a result, military officials had to draw up an operational plan in the midst of a situation that was unfolding rapidly.

Today, regional commands draw up detailed operational plans for a wide variety of contingencies so they will be prepared before a conflict occurs--a lengthy process that can take at least a year to complete. Still, military planners cannot anticipate everything, and conflicts may not follow the script that officials believed they would. Therefore, military commanders would probably prefer DoD to purchase a set of mobility forces that would give them flexibility to change their deployment plans to suit changing conditions.

Certain mixes of mobility forces would limit that flexibility. If DoD relied to a greater extent on prepo-sitioned equipment, for example, military commanders would need to select which units to preposition well before any conflict arose. By contrast, larger investments in airlift forces would provide more flexibility to make last-minute decisions. Thus, another criterion to consider when evaluating alternatives for mobility forces is the amount of flexibility each provides to accommodate changing circumstances.

Vulnerability to Enemy Attack. Most recent DoD studies of mobility requirements have assumed that U.S. deployments would take place in a relatively secure environment--that is, one not under attack. But since the United States would need to move so many forces to fight a major conflict, an enemy would have a strong incentive to slow U.S. deployments by targeting ports and airfields.

To hinder U.S. deliveries, an enemy could mine the waters of ports and harbors, destroy airfield runways, or use missiles or advanced munitions against air or seaport facilities, planes, and ships. As countries continue to develop longer-range missiles, the United States cannot discount the notion that an enemy could target air and seaports with unconventional (chemical, biological, or even nuclear) weapons as well.

Certain types of mobility forces may be more vulnerable to attack than others. Many regions of the world have fewer ports than airfields. Thus, one could conclude that because each LMSR carries such a large concentration of cargo, mining or attacking a major port could lead to greater risk and delays than closing one or two airfields. During Operations Desert Shield and Desert Storm, for example, the United States delivered 96 percent of sealift cargo to just two ports in the Persian Gulf. Airlift deliveries were not quite as concentrated: five airfields accommodated 78 percent of DoD's airlift cargo.(22) Seaports may also provide a more lucrative target for attack than airfields because of the large volume of cargo that ships unload.

Access to critical sea lines, choke points, en route airfields, and the air space of other countries is also an important consideration. For example, if U.S. sealift ships were unable to travel through the Suez Canal on their way to the Persian Gulf, they would have to steam around the southern tip of Africa instead. That would add 3,000 nautical miles to each trip, or five to six more days for an LMSR traveling at 24 nautical miles per hour. Again, airlift is probably less limited by such constraints than sealift, since ships have fewer alternative paths.

Nevertheless, policymakers should keep in mind that for major conflicts, experience from Desert Storm suggests that sealift ships would move more than three-quarters of the total dry cargo. Thus, on the margin, an investment plan that substituted one or two more sealift ships for fewer airlift planes might not make U.S. deployments much more vulnerable to attack.

Flexibility for Delivering Cargo to Smaller Operations

Because of the sheer magnitude of equipment and supplies needed to fight two major regional contingencies, that planning scenario has driven DoD's assessment of its overall requirements for airlift, sealift, and preposi-tioning. But lesser regional contingencies may pose different sorts of problems for strategic lift. For example, the United States may need to deploy into places that are landlocked or far from ports, which would call for more airlift planes or greater use of ground transportation. And unlike Korea or the Persian Gulf region, which have modern airfields and ports, some areas lack long runways, deep ports, and equipment to unload planes and ships.

Planning for those sorts of situations can raise DoD's requirements for planes and ships that have unique military features. Most recently, defense officials looked at examples of smaller operations to decide how many C-17s DoD would need to conduct such missions quickly. Thus, the Congress may want to consider whether alternative investments in mobility forces include enough C-17s to deliver cargo to smaller operations under timelines laid out by DoD. But, as discussed earlier, the exact nature of future missions is highly uncertain. There is also room for debate about whether DoD must precisely meet the timelines set by military planners or whether policymakers are willing to accept a somewhat slower (and thus riskier) deployment.

Peacekeeping Missions, Humanitarian Assistance, and Evacuations of Noncombatants. A 1995 analysis by DoD concluded that 40 C-17s could deliver cargo to any of three representative cases of smaller operations with little risk of an extensive delay. Those cases were taken from the Administration's Defense Planning Guidance; they included a peacekeeping mission, a humanitarian operation, and an evacuation of noncombatants from a foreign country. DoD's analysis did not evaluate how many C-17s the United States would need if it became involved in several cases simultaneously.

Peace Enforcement Missions. The United States may need to deploy larger numbers of troops to enforce a peace between rivals, such as in the current U.S. operations in Bosnia. That type of operation would be smaller than a major regional conflict but might take place under tighter schedules than, say, a peacekeeping deployment, and it would probably involve more troops and heavier equipment to protect them. Thus, peace enforcement missions could place greater demands on airlift and raise requirements for military planes such as the C-17.

In their recent analysis of a representative peace enforcement mission, DoD planners found that an airlift fleet with 72 or 86 C-17s could deploy U.S. forces within a time frame that they characterized as having moderate risk. If the Congress chose to include larger numbers of C-17s in its mobility purchases, that level of risk might fall because the United States could probably conduct the deployment more quickly. Alternatively, DoD could buy fewer than 72 C-17s and accept somewhat slower airlift deliveries to such a mission. Policymakers might find that higher level of risk acceptable if, for example, they believe that the timelines laid out by military planners are too ambitious. Or, as in the 1996 deployments to Bosnia, factors such as bad weather might keep the United States from completing more than a few airlift missions per day, thus keeping commanders from meeting their tight schedules.

Other Special Airlift Missions

In the Administration's 1995 recommendation to buy a total of 120 C-17s, defense officials pointed to certain missions that they believe only the C-17 can accomplish: conducting large airdrops over intercontinental distances, moving key combat units within a theater of operations, and delivering cargo from the United States directly to a battle front. But the C-17's military capabilities come at a high cost. Therefore, the Congress may want to weigh that cost against the likelihood that the United States will need to conduct such special airlift missions in the future.

Long-Range Airdrops of Large Forces. Under DoD's current requirements, the Army must be prepared to deploy brigade-size forces anywhere in the world within a short time frame. To that end, military planners must prepare to air-drop a "medium-force package" consisting of more than 2,500 troops and some of their equipment that have traveled intercontinental distances. (After the airdrop, cargo planes would deliver additional equipment to reinforce those units from airfields that the paratroopers had seized.)

Defense officials believe that once the C-141 is retired from service, DoD will need at least 100 C-17s in its inventory to conduct such a large airdrop at a moderate level of risk. With a smaller number of planes, the United States could not insert its forces as quickly, and thus such a mission would be riskier. Alternatively, defense officials contend, a fleet with 120 C-17s would ensure that DoD could deliver brigade-size forces within the timelines laid out by military planners. Army officials believe that DoD would need at least 120 C-17s for that mission.

But historically, the United States has rarely air-dropped such a large number of paratroopers, and it has not conducted such a mission in distant theaters since Vietnam. (However, DoD has conducted large airdrops over shorter distances into Grenada in 1983 and Panama in 1989, and it was prepared to conduct one into Haiti in 1994.) A brigade-size airdrop over longer distances would be much more demanding and thus, in the opinion of some analysts, an unlikely event. However, other analysts argue that by maintaining the capability to enter other countries forcibly, the United States can deter potential aggressors before they act.

Intratheater Deliveries. Rather than devoting all of DoD's C-17s to strategic airlift, regional commanders would like to devote one or two squadrons to moving key pieces of equipment within a theater of operations. A 1995 DoD analysis concluded that the Air Force could conduct a strategic airlift deployment to DoD's major planning scenarios with mixtures of 86 to 100 C-17s when combined with additional planes like the C-33. If military commanders chose to use some C-17s for intratheater deliveries, however, DoD would need to buy more of those aircraft. In order to use C-17s in that way, some military leaders recommend increasing DoD's planned purchase of 120 planes by 14.

With fewer planes, DoD might not have enough to devote to intratheater deliveries without significantly slowing the pace of deliveries from the United States. Alternatively, military planners could rely on trains and trucks to move outsize cargo, albeit more slowly than by airlift.

Direct Deliveries. Because the C-17 can carry outsize cargo and land at short, ill-equipped airfields, military planners who prepare for combat might prefer that the Air Force deliver cargo directly from the United States close to a battlefield. The Congress may want to consider whether using some C-17s in that way would significantly slow down the pace of deployments from the United States.

According to DoD's analysis, airlift fleets with as few as 72 C-17s, when combined with additional C-33s, would allow the United States to conduct some direct deliveries but still keep an airlift deployment to a major regional conflict going at a pace associated with moderate risk. Fewer C-17s (or fleets with 72 C-17s but no C-33s) would slow that pace and, in the opinion of defense officials, unacceptably raise the risk that DoD could not complete its deliveries quickly enough. Alternatively, DoD could continue to conduct its airlift deployments the way it has in the past: delivering equipment to larger bases farther away from combat and then using trucks, railways, and smaller planes to move the equipment forward.

1. David Kassing, "Strategic Mobility in the Post-Cold War Era," in Paul K. Davis, ed., New Challenges for Defense Planning, MR-400-RC (Santa Monica, Calif.: RAND, 1994), p. 671.

2. Ibid.

3. Congressional Budget Office, Options for Strategic Airlift, CBO Memorandum (October 1995), pp. 4-5.

4. Deborah Christie, former division director for mobility forces, Office of the Secretary of Defense for Program Analysis and Evaluation, as cited in Schuyler Houser, The Congressionally Mandated Mobility Study, Case C16-87-789.0 (Boston, Mass.: Harvard University, Kennedy School of Government, 1987), p. 10.

5. Department of Defense, Office of the Under Secretary of Defense for Acquisition and Technology, Report of the Defense Science Board Task Force on Strategic Mobility (August 1996), p. 11.

6. That incentive has led one mobility planner to characterize what regional commanders would like to send to a conflict as "Star Trek-like requirements that would require a transporter room the size of Rhode Island"; Maj. Kirk A. Yost, "Measuring Pants Legs to the Nearest Inch and Waist Size to the Nearest Foot: Input-Model Disconnects in Airlift Analysis," Phalanx: The Journal of the Military Operations Research Society (December 1995), p. 32.

7. Kassing, "Strategic Mobility in the Post-Cold War Era," p. 679.

8. John Lund, Ruth Berg, and Corinne Replogle, An Assessment of Strategic Airlift Operational Efficiency, R-4269/4-AF (Santa Monica, Calif.: RAND, 1993), p. 13.

9. Houser, The Congressionally Mandated Mobility Study, p. 2.

10. Owen Cote Jr., Strategic Mobility and the Limits of Jointness, Center for Science and International Affairs Monograph (Cambridge, Mass.: Harvard University, forthcoming).

11. Kassing, "Strategic Mobility in the Post-Cold War Era," p. 688.

12. Cote, Strategic Mobility and the Limits of Jointness, pp. 4-11.

13. Department of Defense, Report of the Defense Science Board Task Force on Strategic Mobility, p. 8.

14. Lt. Gen. William G. Pagonis, Moving Mountains: Lessons in Leadership and Logistics from the Gulf War (Cambridge, Mass.: Harvard Business School Press, 1992), pp. 205-206; Lund, Berg, and Replogle, An Assessment of Strategic Airlift Operational Efficiency, pp. 46-47.

15. Department of Defense, Report of the Defense Science Board Task Force on Strategic Mobility, p. 56.

16. James K. Matthews and Cora J. Holt, So Many, So Much, So Far, So Fast: United States Transportation Command and Strategic Deployment for Operation Desert Shield/Desert Storm (Joint History Office, Office of the Chairman of the Joint Chiefs of Staff; and Research Center, U.S. Transportation Command, 1995), pp. 21-22.

17. Ibid., p. 27.

18. Department of Defense, Report of the Defense Science Board Task Force on Strategic Mobility, p. 45.

19. Department of Defense, Joint Chiefs of Staff, Logistics Directorate, Mobility Requirements Study Bottom-Up Review Update Study Plan (July 1994), p. 2.

20. Elaine M. Grossman, "OSD Debates How to Explain Military's Difficulty with Two-War Strategy," Inside the Pentagon, January 26, 1995, pp. 1, 10.

21. Matthews and Holt, So Many, So Much, So Far, So Fast, p. 19.

22. Department of Defense, Report of the Defense Science Board Task Force on Strategic Mobility, p. 56.

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