Moving U.S. Forces: Options for Strategic Mobility Section 2 of 12
February 1997


In the aftermath of the Cold War, some military analysts believe that strategic mobility--the system of equipment, personnel, and logistical know-how for moving military forces over intercontinental distances--is more important than ever before. The Department of Defense (DoD) has reduced the number of U.S. troops stationed abroad, so the United States will need to deploy forces over a longer distance if it becomes involved in a foreign conflict. The ability to project large numbers of forces quickly has been a distinctive feature of the U.S. military. In the opinion of some analysts, it is one means of maintaining the nation's status as a superpower.

The Administration envisions having a smaller, but more flexible, set of forces that the United States could use to counter regional aggressors anywhere in the world. As a result, strategic mobility is a top priority: the Administration proposes to spend nearly $20 billion (in current dollars) between 1998 and 2002 to acquire new cargo planes and sealift ships. That amount constitutes about 7 percent of proposed military procurement spending over the period.

However, spending for strategic mobility will take place during a period of intense competition for funding--both in the defense budget and in the federal budget as a whole. In light of that competition, the Congress may want to consider alternatives to the Administration's plan for mobility forces that would provide similar capabilities at a lower cost. In doing so, policy-makers need to understand the implications of using different modes of lift and how military planners arrived at their numerical requirements for mobility forces. This study examines those issues and evaluates the costs and capabilities of five alternative approaches to modernizing strategic mobility. (The study uses the terms "strategic mobility" and "strategic lift" interchangeably.)

Current Mobility Forces and Requirements

The U.S. military delivers troops and cargo over strategic (that is, intercontinental) distances in three ways: by air, ship, or flying troops abroad to meet up with equipment already stored ("prepositioned") there. Each of those modes has its own combination of strengths and weaknesses. Airlift planes travel very quickly, but their great expense makes them impractical for delivering more than a small portion of cargo in a large-scale deployment. DoD used sealift ships to move more than 70 percent of all dry cargo during the Persian Gulf War, but those ships took three to four weeks to travel from the United States. Prepositioning combines the speed of airlift with the volume of cargo that sealift can provide. But storing military equipment in other countries requires planners to determine ahead of time where conflicts are likely to occur and which units they would deploy first. Moreover, host countries may limit how and where the United States can use that equipment, and large prepositioned U.S. stocks can present an attractive target for potential enemies.

In the past, the United States relied heavily on commercial planes and ships to move its forces. Today, DoD has sizable mobility forces of its own, but it would still need help from participants in the Civil Reserve Air Fleet (CRAF) and the Voluntary Intermodal Sealift Agreement (VISA) during major conflicts. Under CRAF and VISA, commercial companies agree to make planes and ships available to the military during wartime, in exchange for a share of the government's transportation business during peacetime. Those arrangements benefit both the companies and DoD, which would otherwise have to pay for procuring and operating an equivalent number of planes and ships. In recent years, the needs of the military and the commercial transportation sector have diverged somewhat, and DoD has bought its own fleet of planes and ships. But considerable debate still exists about whether DoD needs as large a fleet as it proposes or whether it could broaden its reliance on civil transportation.

Once DoD uses strategic mobility to move forces from the United States to distant theaters, it needs in-tratheater cargo planes, heavy-duty trucks, trains, and smaller watercraft to move those troops and their gear forward to the battlefront. DoD also needs many other components to operate a complete transportation system: skilled personnel to run airfields and ports, computer systems that allow military commanders to communicate their priorities for deploying forces, and a broad array of smaller equipment such as elevator loaders, cargo containers, cranes, and forklifts, to name a few. Investments in those less obvious components of DoD's transportation system can be just as important as the decisions about large planes, ships, and preposi-tioning.

Defense planners have focused increasingly on strategic mobility since the 1990 deployment of U.S. forces to the Persian Gulf for Operations Desert Shield and Desert Storm. In the aftermath of that war, the Office of the Joint Chiefs of Staff concluded that although the deployment was largely successful, those troops who were deployed earliest faced considerable risk, particularly if Iraq had immediately invaded Saudi Arabia. Since then, military planners from the Joint Chiefs of Staff have emphasized the need for deploying heavy ground forces--those with tanks or armored vehicles and lots of firepower--early in a conflict to halt an enemy's advance.

If a conflict broke out in the Persian Gulf today, for example, the Army would try to deploy a full heavy division to the region in about two weeks. That strategy would reduce the risk to U.S. troops who deployed first. And if those early forces were able to halt an attack quickly, the Army's plan could lower the total number of troops the United States would need to send abroad.

But such an approach would place significant demands on U.S. strategic mobility. Indeed, the Army's goals would require DoD's transportation system to deliver a heavy division to the Persian Gulf in about half the time it did in 1990. That task is even harder today because the Army--which defense planners believe would create 77 percent of DoD's mobility workload in a major conflict--requires more floor space and has gotten heavier over time as it has modernized its equipment.

Yet recent deployments to the Persian Gulf, such as Operation Vigilant Warrior in 1994, suggest that DoD may be able to achieve its delivery goals through pre-positioning. Immediately after the Gulf War, the Joint Chiefs recommended that DoD preposition equipment for combat and combat-support units on board ships. Combined with additional brigade-size sets that the Army is prepositioning on land, that equipment might allow military planners to meet their objectives.

The Administration's Plan for Mobility Forces

The Administration would devote most of DoD's funding for strategic mobility to purchasing airlift planes, though it would continue to buy sealift ships as well. At the same time, defense officials recognize how important prepositioning is for their strategy and plan to expand the amount of equipment placed overseas.

Plans for Modernizing Military Airlift and Sealift

A central component of the Administration's plan for mobility forces is the C-17, the Air Force's new cargo plane that will replace the aging C-141. In November 1995, the Administration recommended that the Congress fund a total of 120 C-17s rather than the alternatives it was considering: a mixture of planes with fewer C-17s and either C-5Ds (a new version of DoD's largest airlift plane) or C-33s (a military version of Boeing's 747-400 freighter). Under the Administration's plan for multiyear procurement, C-17 purchases would cost $16.1 billion between 1998 and 2002, with the last planes being bought in 2003 (see Summary Table 1).

The Air Force has already purchased 48 C-17s. Buying 72 more would account for more than a third of the cost of the Administration's plan for strategic mobility between 1998 and 2020, according to the Congressional Budget Office's (CBO's) estimate. Operating and supporting 120 C-17s would cost another

Summary Table 1.
The Administration's Plan for Modernizing Strategic Mobility 
(In millions of 1997 dollars of budget authority)
1997 Total, Total,
and 1998- 1998-
Earlier 1998 1999 2000 2001 2002 2002 2020
   Quantity 48 9 13 15 15 15 67 72
   Acquisition costs 24,868 2,584 3,384 3,433 3,435 3,232 16,067 18,251
   Operation and support costs a n.a. 376 503 597 725 886 3,086 27,240
Large, Medium-Speed
Roll-on/Roll-off Ships
   Quantity 16 2 1 0 0 0 3 3
   Acquisition costs 5,016 628 b 282 c 0 0 0 909 909
   Operation and support costs
      for ships based in
      the United States n.a. 0 12 25 37 46 120 985
Costs of Prepositioning Afloat n.a. 110 132 175 175 175 768 4,101
Costs of Prepositioning in
Korea and the Persian Gulf
   Acquisition costs n.a. 45 0 0 0 0 45 45
   Operation and support and
      military construction costs n.a. 85 105 109 112 112 522 2,707
Total Costs n.a. 3,826 4,418 4,339 4,484 4,451 21,517 54,239
SOURCE: Congressional Budget Office.
NOTES: The costs shown above do not reflect all mobility forces—only those that will vary among the five alternatives presented in this study. For example, 
              the costs do not include operation and support of other cargo planes, such as C-5s and KC-10s, or other sealift ships, such as SL-7s. Nor do they  
              include any additional purchases of smaller roll-on/roll-off ships for the Ready Reserve Force.
             Operation and support costs include the costs of operation and maintenance as well as compensation for associated military personnel.
             n.a. = not available.
a. Includes operation and support costs for the first 48 C-17s. At a steady-state level, those 48 planes (41 primary aircraft authorized) would cost approximately 
    $533 million a year (in 1997 dollars) to operate and support.
b. Includes advance procurement funding for one ship in 1999.
c. For 1997, the Congress added $300 million to the Administration's request in order to speed up the purchase of one ship. As a result, CBO reduced the  
   Administration's plan in 1999 by one ship at a cost of $300 million.

$27.2 billion during that period, bringing the share associated with the C-17 to nearly 85 percent of total costs for the Administration's plan. Because DoD would incur most of the costs of buying C-17s between now and 2002, the plane's share of total costs would be even higher in the near term.

To improve its sealift capacity considerably, the Administration also plans to buy a total of 19 large, medium-speed roll-on/roll-off ships (LMSRs). Eight of those vessels would be used to preposition equipment for heavy forces and support units; the other 11 would transport equipment from the United States (so-called surge sealift). To meet that plan, DoD would acquire three more LMSRs in 1998 and 1999 at a total cost of $909 million. The Administration is also examining ways to add capacity to its fleet of smaller roll-on/roll-off ships in the Ready Reserve Force. (The Ready Reserve Force is a fleet of inactive cargo ships maintained by the Department of Transportation's Maritime Administration. In the event of a conflict, those vessels would supplement DoD's other sealift ships.)

Summary Figure 1.
The Administration's Plan to Preposition Equipment for Two Major Regional Conflicts

SOURCE: Congressional Budget Office.

NOTE: MPS = Maritime Prepositioning Ships; LMSR = large, medium-speed roll-on/roll-off ship; DLA = Defense Logistics Agency.


Plans to Expand Prepositioning

In its most recent comprehensive military plan--the 1993 Bottom-Up Review--DoD focused on a scenario in which the United States would fight two nearly simultaneous major conflicts (or contingencies, as DoD calls them) on the Korean Peninsula and in the Persian Gulf region. As a result, DoD has begun preposition-ing equipment in those areas.

Current plans call for the Army to preposition enough equipment for two heavy brigades and a divisional headquarters in the Persian Gulf region over the next several years (see Summary Figure 1). (A brigade is roughly one-third the size of a division.) The Air Force has prepositioned equipment in the Persian Gulf as well: materiel that would allow it to set up and operate air bases quickly in the event of conflict. In South Korea, the Army recently prepositioned tanks and armored fighting vehicles for one heavy brigade. Since the Army already has two manned heavy brigades stationed there, the additional equipment would help provide a complete division quickly if war broke out.

Both the Marine Corps and the Army intend to expand the amount of equipment that they have preposi-tioned on ships, which DoD could send to any number of contingencies. The Marines plan to add one ship to each of three existing squadrons of vessels located in the Mediterranean, at Diego Garcia in the Indian Ocean, and at Guam and Saipan in the Pacific. Each extra ship would hold equipment for an expeditionary airfield, a fleet hospital that would be set up on land, a construction battalion, and headquarters units to support Marine operations. In 1993, the Army began placing equipment for a heavy brigade and support units on seven roll-on/roll-off ships anchored at Diego Garcia. DoD planners expect to replace those ships with eight LMSRs by the end of the decade, more than doubling the amount of cargo space available.

Evaluating Requirements for Strategic Mobility

DoD bases its numerical requirements for strategic mobility forces on a 1995 analysis called the Mobility Requirements Study Bottom-Up Review Update (MRS BURU). That study closely followed the assumptions of the two-war planning scenario outlined in the Bot-tom-Up Review.

The recommendations of the study supported some positions that were already part of the Administration's plans. For example, the study reinforced an earlier recommendation by the Joint Chiefs of Staff to buy 19 LMSRs and smaller roll-on/roll-off ships, which would allow the Army to expand its afloat prepositioning program and also provide DoD with considerably more capacity to carry cargo on ships from the United States. When the MRS BURU was published, the Administration had not yet decided whether to follow through on an earlier decision to buy 120 C-17s or instead purchase a mixture of C-17s and other airlift planes. However, the recommendations of the MRS BURU about airlift were consistent with what the Air Force would achieve if it added 120 C-17s to its fleet.

How do planners decide what type and amount of strategic lift is best? The authors of the MRS BURU first identified how much force they believed the United States would need to halt enemy assaults on the Korean Peninsula and in the Persian Gulf region. Using computer simulations of combat, the Joint Chiefs of Staff and other DoD analysts tried to establish when certain units would need to arrive in order to limit the amount of risk faced by the forces who deployed earliest. Then, using simulations of cargo deliveries, they determined what combinations of mobility forces would allow DoD to meet those timelines.

Every analysis of mobility requires a vast number of assumptions. Those assumptions can be grouped in three broad categories: the nature of whom the United States would need to fight and how that foe might prosecute an attack; which U.S. forces would be sent to the conflict and whether they would be ready to deploy; and whether military and commercial planes and ships would be available and would operate as expected. So much uncertainty surrounds each of those issues that there is room for debate over almost any assumption that planners make. Probably no mobility analysis can definitely settle how much lift is enough and what com-bination of mobility forces best suits the needs of the United States. Ultimately, that is a subjective judgment in which decisionmakers must balance the cost of investing in mobility forces against the capabilities that those forces would provide.

Besides uncertainty, another problem inherent in determining lift requirements is that planning for a major deployment involves two very different communities of military analysts: those who prepare for combat operations and those who plan to deliver the forces. Historically, warfighters and mobility planners have approached their task from widely different viewpoints. Warfighters, such as regional commanders, face the consequences of risk most directly, so they make plans to deploy a large enough force to ensure dominance on the battlefield.

Mobility planners, less directly exposed to risk, tend to use fairly optimistic assumptions about what the United States could deliver early in a conflict. In the MRS BURU, for example, mobility planners assumed that reserve personnel would be called up quickly, that the weather would be clear, and that DoD would supplement its military airlift and sealift fleets quickly with commercial transportation. One assumption to which the MRS BURU is perhaps most sensitive is that deci-sionmakers would receive unambiguous warning of an attack and then act quickly on that intelligence. Unfortunately, history is replete with examples of how leaders saw warnings of an impending attack and yet failed to act.

Options for Modernizing Strategic Mobility Forces

In order to look at different approaches to strategic mobility, CBO developed five alternatives to the Administration's plan. The options represent only marginal changes from that plan because they all propose continuing to purchase mobility forces for the military rather than expanding commercial transportation programs. The options also have the vast majority of strategic mobility forces in common, including airlift planes such as the C-5 and KC-10, SL-7 fast sealift ships, other roll-on/roll-off vessels from the Ready Reserve Force, and commercial planes and ships.

Four of the five alternatives would cost significantly less than the Administration's plan because they would substitute prepositioning, sealift, or less expensive airlift planes for purchases of C-17s (see Summary Table 2). CBO also included one alternative in which DoD would buy a larger number of C-17s than under the Administration's plan but would simultaneously reduce the amount of equipment it prepositioned afloat.

Option I: Buy Fewer C-17s and Preposition More Equipment Afloat

Under the first alternative, DoD would purchase a total of 72 C-17s rather than 120. In place of airlift, Option I would substitute one additional LMSR that DoD would use to keep a larger amount of equipment prepositioned afloat.

How can one LMSR substitute for 48 planes? Each new vessel can preposition at least 250,000 square feet of cargo (after adjusting for reserve stowage space). By contrast, each C-17's cargo hold can carry approximately 1,500 square feet. It would take a total inventory of 38 to 52 C-17s to deliver 250,000 square feet of cargo from the United States to the Persian Gulf in the same amount of time as one LMSR steaming there from Diego Garcia and unloading its cargo (about 11 to 12 days). In fact, that number understates the comparison: airlift loads are constrained more by the weight and three-dimensional shape of their cargo than by floor space. So one LMSR prepositioned abroad could quite arguably replace airlift deliveries by 48 C-17s over the first two to three weeks of a major regional conflict.

The Army already plans to preposition much of its heaviest equipment, but it may be able to do more. For example, at least half of the weight associated with Army aviation units comes from trucks, trailers, and other vehicles that could be stored on an LMSR. Similarly, the Air Force deploys most of its cargo by airlift, including heavy equipment for engineering units that could be prepositioned. For Option I, CBO identified nearly 260,000 square feet (or 11,400 tons) of equipment that DoD could preposition on board an additional LMSR--or roughly 14 percent to 19 percent of the total amount that would otherwise be airlifted during the first two to three weeks of a major conflict.

Under Option I, the Navy and the Army would face higher costs associated with buying one additional ship and another set of equipment. CBO also assumed that the average cost of purchasing C-17s would be higher if the Air Force bought just 72 rather than 120. Nevertheless, CBO estimates that Option I would cost $18.2 billion less than the Administration's plan over the 1998-2020 period. More than $7 billion of those savings would accrue by 2002 (see Summary Table 3).

Option II: Buy Fewer C-17s and Preposition More Equipment on Land

CBO's second alternative is similar to Option I in that DoD would limit its C-17 purchase to 72 planes. Rather than expanding prepositioning on ships, however, Option II would preposition more equipment in warehouses erected both in South Korea and in the Persian Gulf region. The services would need to purchase two extra sets of equipment--one for each location--so Option II would actually cost slightly more than Option I, even though DoD would not be buying an additional LMSR. But DoD could tailor the prepositioned sets for the scenario at hand, including important equipment, such as that to support a Patriot air-defense artillery battalion, that DoD believes does not stand up well to prepositioning at sea.

CBO estimates that the savings associated with a smaller airlift purchase would far outweigh the added costs of building warehouses, buying extra equipment,

Summary Table 2.
Five Alternatives for Modernizing Strategic Mobility
Land-Based  Afloat
Option Airlift Prepositioning Prepositioning Surge Sealift
Administra- 120 C-17s Two heavy-brigade sets  One heavy-brigade 11 LMSRs
tion's Plan in the Persian Gulf, set and support units
one in South Korea on board eight LMSRs
I 48 fewer C-17sa Same as Administra- One more LMSR Same as Administra-
tion's plan tion's plan
II 48 fewer C-17sa Adds 240,000 square Same as Administra- Same as Administra-
feet of prepositioning in  tion's plan tion's plan
both the Persian Gulf 
and South Korea
III 48 fewer C-17s,a Same as Administra- Same as Administra- Same as Administra-
adds 30 C-33sb tion's plan tion's plan tion's plan
IV 20 more C-17sc Same as Administra-  One fewer LMSR Same as Administra-
tion's plan tion's plan
V 48 fewer C-17sa Same as Administra- Same as Administra- One more LMSR
tion's plan tion's plan
SOURCE: Congressional Budget Office.
NOTE: LMSR = large, medium-speed roll-on/roll-off ship.
a. A total of 72 C-17s, or 61 primary aircraft authorized.
b. A total of 30 C-33s, or 27 primary aircraft authorized.
c. A total of 140 C-17s, or 119 primary aircraft authorized.

Summary Table 3.
Comparison of the Costs and Capabilities of Alternatives for Modernizing Strategic Mobility
Administra- Option
tion's Plan I II III IV V
Cumulative Costs (In billions of 1997 dollars)
      Total 21.5 14.4 15.1 17.5 21.3 14.0
      Savings from the Administration's plan n.a. 7.1 6.4 4.0 0.2 7.5
      Total 54.2 36.1 37.5 45.8 60.5 35.3
      Savings from the Administration's plan n.a. 18.2 16.8 8.4 (6.3) 18.9
Cumulative Airlift Deliveries to the
Persian Gulf Plus Sustainment to Korea
(In thousands of tons) a
   By day 20, including
      incremental prepositioning b 119.9 123.1 123.0 114.6 117.6 111.6
   Difference from the Administration's plan n.a. 3.1 3.1 (5.3) (2.4) (8.3)
Outsize Airlift Deliveries to Korea
(In thousands of tons) c
   By day 20 22.0 20.8 20.8 21.8 27.8 20.8
   Difference from the Administration's plan n.a. (1.2) (1.2) (0.3) 5.7 (1.2)
Flexibility to Handle Changes in Very Less Least Very Most Flexible 
Deployment Schedules flexible flexible flexible flexible flexible but slow
Vulnerability to Enemy Attack Less More Most Less Least More
vulnerable vulnerable vulnerable vulnerable vulnerable vulnerable
Risk Associated with Cargo Deliveries
to Smaller Operations d,e
   Peacekeeping missions, humanitarian
      assistance, and evacuations Low Low Low Low Low Low
   Peace enforcement missions Low Moderate Moderate Moderate Low Moderate
Risk Associated with Special Airlift Missionsd
   Strategic brigade airdrops e Low High High High Low High
   Intratheater unit moves Low High High High Low High
   Direct delivery Low High High High Low High
SOURCE: Congressional Budget Office.
NOTE: n.a. = not applicable.
a. While deploying forces by air to the Persian Gulf, cargo planes would also continue airlift operations on a smaller scale to the Korean Peninsula. The values  
    shown here include airlift deliveries to Korea that would occur at the same time as the deployment to a second conflict in the Persian Gulf. They include  
    airlift deliveries for flexible deterrent options in the Persian Gulf region.
b. For two of the alternatives, CBO included deliveries of 11,400 tons of additional equipment prepositioned either afloat (Option I) or on land (Option II). For  
    deliveries under Option IV, CBO subtracted 11,400 tons to reflect one fewer large, medium-speed roll-on/roll-off ship used for afloat prepositioning.
c. Includes deliveries for flexible deterrent options.
d. Risk in this case refers to risk of failing to complete the delivery mission in the required time.
e. CBO was unable to independently assess the risk associated with these missions. The levels shown are based on Defense Department analysis.

and guarding and maintaining it. Net of those costs, Option II would save $16.8 billion compared with the Administration's plan over the 1998-2020 period, or $6.4 billion through 2002.

Option III: Buy a Mixture of Airlift Planes

Under the third alternative, DoD would acquire the same theoretical airlift capacity that 120 C-17s provide but with a less expensive mixture of planes: 72 C-17s plus 30 modified commercial wide-body jets like the C-33. Each C-33 can hold more cargo than a C-17, but the latter can carry a wider variety of military equipment because of the larger width and height of its doors and cargo hold. Nevertheless, this option would give DoD a comparable level of theoretical airlift capacity as the Administration's plan. (Theoretical airlift capacity measures the amount that all airlift planes in a fleet could carry when fully mobilized, using average measures of each plane's performance. Actual airlift deliveries tend to be lower than theoretical capacity.)

Under Option III, DoD would buy C-17s at a rate of just eight per year. Thus, the average cost of those planes would be higher than under the Administration's plan, in which DoD would purchase C-17s at a maximum of 15 per year. Nevertheless, CBO estimates that Option III would cost $8.4 billion less than the Administration's plan over the 1998-2020 period--nearly $4 billion less over the first five years.

Option IV: Buy More C-17s and Preposition Less

To demonstrate all of the trade-offs between preposi-tioning and airlift, Option IV is the reverse of Option I: it would add airlift to the Administration's plan and subtract prepositioning ships. Specifically, Option IV would buy a total of 140 C-17s rather than the 120 the Administration intends but one fewer LMSR for afloat prepositioning. That larger number of C-17s would give DoD about 7 percent more theoretical airlift capacity from its own fleet than the Administration's plan would.

Because airlift is so much more expensive than other modes of lift, the cost of a larger number of C-17s would far surpass the savings associated with one fewer LMSR. CBO estimates that Option IV would cost roughly the same as the Administration's plan between 1998 and 2002 but $6.3 billion more than the plan through 2020.

Option V: Buy Fewer C-17s and More Surge Sealift

The fifth alternative would once again limit DoD's C-17 purchases to a total of 72, but in the place of airlift, it would buy an additional LMSR that DoD would use to surge cargo from the United States during wartime. Compared with ships prepositioned in the Indian Ocean, surge sealift vessels would have a longer distance to travel, so Option V would not permit DoD to complete deliveries as quickly as Option I, whose forces are identical. But if DoD's assumptions about how much equipment it could deliver quickly by airlift and prepositioning are implausible, Option V may be more practical.

Option V is the least costly of the alternatives. CBO estimates that it would save $18.9 billion compared with the Administration's plan over the 1998-2020 period and $7.5 billion between 1998 and 2002. Through 2020, it would also cost $746 million less than Option I.

Comparing the Capabilities of the Alternatives

The Congress might want to consider three categories of capabilities when comparing options for strategic mobility: how well each alternative delivers cargo to two major regional conflicts, how much flexibility each provides for delivering cargo to smaller contingencies, and how well each performs special airlift missions.

Cargo Deliveries to Major Regional Conflicts

Because DoD's plan to fight two major regional contingencies is so demanding, CBO estimated how much each option could deliver in that scenario. Specifically, CBO focused on what the MRS BURU considered the most taxing conditions for mobility forces: a war in the Persian Gulf region that broke out shortly after one in the Korean Peninsula. CBO estimated how much equipment each option could deploy during the halting phase of a conflict in the Gulf (roughly the first two to three weeks, in DoD's assessment) while still delivering supplies to Korea to sustain operations there.

One recommendation of the MRS BURU was to devote one LMSR or two smaller roll-on/roll-off ships to additional prepositioning rather than to surge sealift. However, since DoD has not yet carried out that recommendation or included the necessary funding in its budget requests, CBO did not consider that additional pre-positioning to be part of the Administration's plan. If defense officials carried out the recommendation in the future, DoD would be able to deliver considerably more equipment during the halting phase of a major regional contingency. As a result, those alternatives that include additional prepositioning (Options I and II) or that emphasize surge sealift (Option V) would compare much less favorably with the Administration's plan than they do here.

CBO's analysis suggests that the alternatives that emphasize prepositioning, Options I and II, might allow DoD to deliver slightly more equipment over the first two to three weeks of deliveries. But that margin is small: just 3,100 tons, or about 3 percent of total airlift deliveries that the Administration's plan might achieve over the same period (see Summary Figure 2).

Based on CBO's analysis, Options III, IV, and V would each deliver less cargo early in a second regional contingency than the Administration's plan. In Option III, the larger size of commercial wide-body jets could constrain their use if airfields were congested, so that alternative might deliver roughly 4 percent less in three weeks than a plan with 120 C-17s. Option IV includes 140 C-17s and thus it can deliver more by airlift. But the additional planes would not make up for having one fewer LMSR, and CBO estimates that Option IV would deliver about 2 percent less cargo than the Administration's plan. Since Option V includes fewer airlift planes and no additional prepositioned equipment, it would deliver the least amount of cargo early in a second major contingency--roughly 7 percent less than the Administration's plan.

Compared with requirements during the Cold War, today DoD plans to send relatively less outsize cargo by airlift. (Outsize is the term DoD uses to describe the largest pieces of cargo, which can fit only on C-17 or C-5 aircraft.) Yet some analysts believe that having larger numbers of planes that can carry outsize cargo is important so military commanders can keep their units together during a deployment. For that reason, CBO also analyzed how well each option could deliver outsize cargo in the scenario that, according to DoD officials, would feature the most congested airfields: a major conflict on the Korean Peninsula.

Summary Figure 2.
Airlift Deliveries to a Conflict in the Persian Gulf, Plus Sustaining Operations in Korea, Under the Administration's Plan and Five Alternatives (In thousands of tons delivered)

SOURCE: Congressional Budget Office.

a. Because Option IV includes one fewer large, medium-speed roll-on/roll-off ship than the Administration's plan, it would need to deliver additional cargo by airlift that would otherwise have been prepositioned. As a result, Option IV would deliver about 2,400 tons less by day 20 than the Administration's plan.

b. The total amount of prepositioned equipment that the military would deliver to a major regional conflict is classified information, so the prepositioning shown here is the amount that CBO added to or subtracted from the Administration's plan.

Among the five alternatives, only Option IV could deliver more outsize cargo than the Administration's plan. CBO estimates that the larger number of C-17s under that option might allow DoD to deliver 26 percent more outsize equipment over the first 20 days of a Korean deployment. Even with wider doors and strong floors, commercial jets like the C-33 cannot carry most types of outsize equipment. Nevertheless, CBO estimates that Option III would deliver just 1 percent less over the first three weeks of deployments than the Administration's plan. Options I, II, and V would each deliver about 6 percent less outsize cargo because of their smaller number of airlift planes.

In addition to how quickly each option delivers cargo, the Congress might want to consider other characteristics of the different modes of lift. For example, if DoD relied more heavily on prepositioned forces (as in Options I and II), military commanders would need to decide far in advance of a conflict which units they planned to deploy first. Although that arrangement would reduce the demands on DoD's transportation system, it would not allow commanders to change their deployment plans as the situation unfolded. Alternatives that include more airlift (like Options III and IV) might provide flexibility for last-minute changes to the deployment schedule, so long as the adjustments did not call for sending heavy forces.

Some types of mobility forces could also be more vulnerable to attack than others. An enemy wishing to slow the pace of deployments from the United States would be wise to target both airfields and ports. But most countries have more airfields than ports, and therefore it might be harder for an enemy to predict precisely where the United States would send its airlift planes. Moreover, the larger concentrations of cargo on ships and in prepositioning warehouses probably makes those modes somewhat more vulnerable to attack than airlift planes.

Flexibility for Delivering Cargo to Smaller Operations

Smaller military operations can pose different sorts of problems for strategic mobility than major regional conflicts. For example, such operations would probably take place without reserve personnel or the Civil Reserve Air Fleet being activated. There are also more regions where the United States might need to become involved in smaller operations, including countries that are landlocked or that lack modern airfields. Thus, the Congress might want to consider how well various investments in mobility forces would perform in those sorts of scenarios.

To examine that issue, CBO applied the results of a 1995 DoD study of smaller contingencies to each of its five alternatives. DoD's analysis examined how quickly airlift fleets that included different numbers of C-17s could deliver cargo to smaller operations and how well they could perform special airlift missions. Because of the large number of classified assumptions about where those operations would take place and how they would proceed, CBO was unable to conduct a similar independent analysis. Thus, readers should bear in mind that the assessments of risk presented here are largely those of DoD, and its analysis is subject to the uncertainties described earlier.

The DoD study looked at four representative situations in which the United States might need to deliver cargo short of a major regional conflict: a peacekeeping mission, a humanitarian operation, an evacuation of noncombatants from a foreign country, and a peace enforcement operation. DoD analysts concluded that for the first three categories, airlift fleets with as few as 40 C-17s could complete deliveries with little risk of falling behind the timelines set by military planners. Based on that finding, the Administration's plan and all five of CBO's options could conduct similar types of operations with low risk.

Peace enforcement operations, however, such as the recent deployment of U.S. forces to Bosnia, could be more demanding. In that type of situation, military troops would not operate in as secure an environment. Thus, DoD would need to deploy heavier equipment to protect U.S. troops from the warring parties, and it might need to do so on a quicker schedule. For those reasons, DoD concluded that an airlift fleet with 72 or 86 C-17s would face a moderate risk of completing deliveries too slowly, whereas a fleet with 100 or more C-17s would have a low risk. Is a moderate amount of risk acceptable? Opinions will undoubtedly differ. But in other analyses, such as the MRS BURU, the Joint Chiefs of Staff argued that a moderate level of risk was acceptable given budget constraints.

Other Special Airlift Missions

The Administration points to special additional types of airlift missions for which DoD would need larger numbers of C-17s. One example is a strategic brigade airdrop, in which the United States would need to deploy roughly 2,500 paratroopers and their equipment quickly into hostile territory far from the United States. DoD officials argue that they would require at least 100 C-17s to perform such a mission under the tight timelines laid out by military planners, and Army officials contend that the Air Force would need 120 C-17s to meet their requirement. Thus, if one believes that the United States will need to use that capability in the future, DoD's analysis would place a lower bound on the number of C-17s that it must buy.

Historically, however, the United States has performed very few airdrop operations, and it has conducted none outside the Western Hemisphere since the Vietnam War. A brigade-size intercontinental airdrop would be more demanding than operations like those into Grenada in 1983 and Panama in 1989, since the large number of parachutists would fly for many hours over longer distances, conduct a parachute assault to seize an airfield, and then prepare to receive reinforcements through traditional airlift deliveries. The difficulties of such an operation have led some defense analysts to deem it a highly unlikely event. Other analysts, however, contend that retaining such a capability would deter potential aggressors.

Another mission that might require more C-17s is moving key pieces of outsize equipment within a theater of operations in the midst of a major deployment. Without more planes, devoting one or two squadrons of C-17s to such intratheater airlift could slow the pace of deliveries from the United States. Based on its 1995 analysis, DoD officials argue that a fleet with 86 C-17s and 30 C-33s could complete strategic deliveries for a major conflict in a timely manner. But if military commanders chose to use C-17s for moving cargo within a theater, fewer of those planes would be available to transport forces from the United States, and thus the deployment would take more time. As a result, some military leaders recommend buying 14 additional C-17s for intratheater deliveries. Of course, DoD could continue to rely on trains, trucks, or in some cases smaller watercraft to move outsize cargo within a theater, as it has for years.

One final type of special airlift mission is direct delivery, in which cargo planes fly from the United States directly to airfields close to the battlefront rather than to larger staging bases at the rear of operations. DoD concluded in its 1995 analysis that fleets with at least 72 C-17s (when combined with C-33s) would still allow the United States to deliver some equipment directly to the front. But such a fleet would complete those deliveries more slowly than one with 120 C-17s, and thus the risk associated with having just 72 C-17s would be higher. In the opinion of DoD officials, fewer C-17s would raise the risk of such missions unacceptably, whereas larger numbers (as in the Administration's plan and Option IV) would reduce that risk. Alternatively, DoD could continue to conduct airlift deliveries as it has in the past: by delivering equipment to staging bases by air and then moving it to the battle- front by means of trucks, railways, smaller cargo planes, or watercraft.

Based on DoD's analysis, then, alternatives that include just 72 C-17s (Options I, II, III, and V) might not be adequate to conduct special missions like strategic brigade airdrops and intratheater deliveries. However, airlift is the most costly mode of lift, and the C-17, although a very capable plane, is also quite expensive. Thus, the Congress may want to balance the cost of larger numbers of C-17s against the likelihood that the United States will need to perform the types of special airlift missions for which they are necessary.

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