by John B. Wilson

This article is derived from an information paper Mr. Wilson prepared in December 1995.

In military parlance "division" means different things at different times. In the U.S. Army in the twentieth century, however, the term has been applied to a unit made up of various arms and services, capable of sustained independent operations. The characteristics of those combined arms and services and their ability to conduct sustained operations are key to understanding the nature of the division.

Following a dismal showing in the Spanish-American War of 1898, the Army re-examined its organizations and developed plans for permanent combined arms divisions. These new units were to aid in training (particularly for senior officers) as well as in mobilization. The planners relied heavily on European experiences, even though European nations conducted their training at the corps level. Judging a 35,000-man corps too large an echelon, U.S. Army planners instead designed a division consisting of three infantry brigades, a cavalry regiment, an engineer battalion, a signal company, and four field hospitals. Nine field artillery batteries, organized as a provisional regiment, were also included. To attain a self-sufficient combined arms team, these planners then added an ammunition column, a supply column, and a pack train--all to be manned by civilians. The division had no fixed strength, but in march formation was estimated to use fourteen miles of road space, a distance that represented a day's march for troops and the distance that the last soldier in a column had to cover to reach the battlefront. The limiting factors of the day clearly were those of time and distance.

As plans for the division evolved, the General Staff pioneered tables of organization for all types of units. Forerunners of those used today, the 1914 tables brought together for easy comparison a mass of information about unit personnel and equipment. These data, which previously had been buried in various War Department publications, greatly eased the task of determining mobilization requirements. In addition, the tables served as doctrinal statements and provided a systematic method for introducing new equipment into units. The Field Service Regulations that accompanied the tables defined the division as "a self-contained unit made up of all necessary arms and services, and complete in itself with every requirement for independent action incident to its operations." As war raged in Europe in 1917, the War Department revised the structure of the division, but retained a triangular configuration to provide two combat teams for maneuver and one for reserve.

British and French experiences in World War I, however, revealed that the American division lacked firepower and presented command and control problems because of its many small units. To overcome these difficulties, a division was created comprised of two infantry brigades, each having two large infantry regiments (as a means of reducing the span of control), light and heavy artillery, signal and engineer troops, and service units. Such a division presumably would allow greater mobility, enhance the commander's ability to exchange units in the line, and maintain battle momentum. The French and the British had found that for each unit in the line--army corps, division, brigade, regiment, battalion, or company--a comparable unit was needed to relieve it without mixing organizations from various commands. The new division appeared to ease the difficulty of exchanging units on the battlefield. On 8 June 1917, the Army's first permanent division, the 1st Expeditionary Division, was organized.

Before the organization of the 1st Expeditionary Division had been field tested, two new groups initiated additional studies. Maj. Gen. John J. Pershing, who had been appointed commander of the American Expeditionary Forces (AEF), headed one group, and Col. Chauncey Baker, an expert in military transportation and a West Point classmate of Pershing, headed the other. During the course of their work, Pershing and Baker reversed the rationale for the division. Instead of a mobile organization that could easily move in and out of trenches, the division was to field sufficient men to fight prolonged battles; that is, seize and hold ground and continue the advance. Both planning groups sensed that the French and British wanted that type of division, but lacked the resources to field it because of the extensive losses after three years of warfare. To sustain itself in combat, the division needed more--not less--combat power. When their recommendations reached Washington in July 1917, the Chief of Staff (CSA) acquiesced because Pershing would command the divisions sent to Europe. The lack of experienced staff officers for divisional units and staffs also made a smaller number of large divisions more practical. The new divisional structure, officially adopted on 8 August 1917, was known as the "square division." It eventually consisted of about 28,000 officers and enlisted men.

Designed to conduct sustained frontal attacks rather than to maneuver, the square division was thought to possess tremendous firepower and endurance. The division's firepower, however, proved ineffective. The lack of reliable communications equipment, and the difficulty of identifying the continual movement of infantry units in the offensive, hindered coordination between infantry and artillery, thereby slowing or halting the offensive. Furthermore, the French transportation network was overwhelmed by the logistics requirements for a square division. American divisions in the line suffered from shortages in food, ammunition, and other supplies. Part of the logistical problem also rested with the division's lack of combat service troops to carry rations, bury the dead, and evacuate casualties.

Despite these difficulties, World War I demonstrated the need for greater coordination among the arms and services. Infantry could not advance without support from engineers and artillery; artillery could not continue to fire without a constant supply of ammunition. Transportation and signal units provided vital materiel and command connections, and medical units administered to the needs of the wounded. The complex type of combined arms unit integrating these features became possible because of advances in technology, weapons, communications, and transportation.

Following World War I, the Army leadership reevaluated the divisional organization. Officers from the AEF endorsed the World War I square division and recommended that it be organized to meet varying combat and terrain conditions encountered in maneuver warfare, but with only those elements it customarily needed. Who the next foe might be--and where--posed a problem that haunted divisional planners then, as today. They envisioned a square division numbering 29,000 officers and enlisted men. Although Pershing temporarily shelved the report, Congress and the War Department continued to explore postwar Army organizations. One of their findings was that when the Army was stationed at small, scattered posts, officers had no occasion to command brigades or divisions, thereby gaining experience in managing large troop concentrations. They proposed permanent divisions in which officers could have the opportunity to command large units and to train combined arms units for war, thus correcting a major weakness of past mobilizations. To improve mobilization, Congress required that the Army, as far as practical, be organized into brigades, divisions, and army corps.

To execute the congressional directive, a General Staff committee examined the structure of the division and prescribed a square organization patterned after the unit of World War I. Pershing objected, wanting a more mobile division with a single infantry brigade of three infantry regiments, an artillery regiment, a cavalry squadron, and combat support and combat service support units. Pershing felt the AEF officers undertook their work too soon after the close of hostilities and that their report suffered unduly from the special circumstances of the Western Front. Summarizing the requirements for the infantry division, he wrote: "The division should be small enough to permit its being deployed from . . . a single road in a few hours and, when moving by rail, to permit all of its elements to be assembled on a single railroad line within twenty-four hours." Again, time and distance factors, expressed in tactical terms, determined his concept of the future division.

Ultimately a compromise emerged. The argument for three versus four infantry regiments in the division focused on the division's probable area of employment, North America. Experts deemed another war in Europe unlikely and doubted that the Army would again fight on a battlefield like that seen in France. They felt technological advances in artillery, machine guns, and aviation made obsolete stabilized and highly organized defensive lines whose flanks rested on impassable obstacles, such as those encountered on the Western Front. Because of the poor road network and broken terrain of North America, the committee insisted that only the square division had sufficient mobility and striking power to fight in such an environment, although acknowledging such a vast formation lacked the flexibility of Pershing's suggested unit. Divisional support troops were reduced, but were included at the corps and army levels.

January 1929 marked the beginning of a ten-year struggle--dictated by events in Europe--to reorganize the infantry division. General Staff members reported that European countries were conceptualizing armies that could trigger a war of greater velocity and intensity than anything previously known. The British, French, and Germans were engrossed with "machines" to increase mobility, minimize losses, and prevent stabilization of the battle front. The British concentrated on mechanization and the French on motorization, while the Germans developed concepts that combined aspects of both. In the United States, the Army Chief of Staff agreed to a new divisional study, but because of the vast number of weapons and equipment left from World War I and because of a lack of other resources, the planners were limited to using approved standard infantry weapons, animal-drawn combat trains, and motorized field trains for their design. No restriction was placed on road space, a principal determinant of divisional size before and immediately after World War I. Several proposals surfaced for a triangular infantry division, which promised greater maneuverability, better command and control, and simplified communications and supply. Because of resource constraints, however, no divisions were reorganized.

In 1935 the General Staff revived the idea of examining the division. The Chief of Staff canvassed senior commanders regarding organizational issues, noting that the infantry division had foot, animal, and motor units, all with varying rates of speed, which did not meet the demands of modern warfare. Lacking consensus, the CSA created the Modernization Board to examine the organization of the Army. Despite a broad charter, the board addressed only the infantry division, concluding that the formation of higher commands rested upon the structure of the infantry division.

The end result of this study was the replacement of the square division with a triangular one. An infantry division with three combat teams simplified command structure and provided more flexibility. The elimination of the brigade echelon for infantry and field artillery enabled the division commander to deal directly with infantry regiments and field artillery battalions. The artillery consisted of three direct support battalions of newly-developed 105-mm. howitzers and a general support battalion of 155-mm. howitzers. To assist in moving and operating on a broad front, a cavalry reconnaissance troop equipped with lightly armored cross-country vehicles was assigned to the division. Engineer, signal, quartermaster, military police, medical, and maintenance resources were organized to support the arms. Modern technology brought about significant changes in divisions, one of the more obvious being the elimination of all animal transport, except in a few specialized cases. The newly-developed airborne division was also based upon triangular structure, but fielded fewer men and lighter equipment to accommodate existing aircraft--a variation of the space, distance, and time factors.

The triangular division did not prove to be completely satisfactory during World War II because it lacked all the resources regularly needed to operate efficiently, particularly tank, tank destroyer, and anti-aircraft artillery battalions. Although the Army's goal was to pool these resources at corps level for attachment to division as required, shortages in tank and tank destroyer units made them unavailable to serve regularly with the same division. This resulted in considerable shuffling of attached units, which in turn diminished effective teamwork. Divisional reconnaissance suffered because the armored cavalry troop lacked sufficient strength and its vehicles were too lightly armored and armed for its mission.

The quick success of the German Blitzkrieg into Poland in 1939 had a profound effect on the adoption of a new type of division. Testing of mechanized cavalry and tanks had been ongoing throughout the interwar years on a limited level, but German successes and the U.S. Army maneuvers of 1939-40 resulted in the adoption of true armored divisions. The division was designed as a powerful striking force to be used in rapid offensive action, and its ability for sustained action was an important feature. The first concept saw the division divided into five elements: command, reconnaissance, striking, support, and service. Based upon combat experiences, it was reorganized in 1942 with two armored regiments under two combat commands, with a division artillery similar to that in the infantry division. Another reorganization in 1943 eliminated the two armored regiments, leaving it with three tank battalions and three infantry battalions. A third command was added to control the division reserve on the march, but eventually came to be a third combat command. The heavy division of 1942 was capable of more sustained action, but weak in infantry. The lighter division of 1943 was more balanced in infantry, but needed an additional rifle company to form balanced tank-infantry teams.

Following World War II the Army again examined the infantry division, raising many of the same weaknesses identified during the war. Nevertheless, the division's three regimental combat teams were preserved, with the addition of those units regularly attached in combat. One controversy that affected the development of the infantry division was the postwar battlefield's greater depth and breadth. This "modern" battlefield made conducting reconnaissance and collecting intelligence much more difficult. The answer seemed to be aerial reconnaissance, and indeed ten airplanes had been assigned to the division artillery in 1943 to direct artillery fire. The Army Air Forces opposed the idea of organic aviation units in the division. Airmen argued that all air units had to come under their jurisdiction. No aviation unit was assigned to the postwar division, although ten planes were authorized for the field artillery and eight to the division headquarters company. The modified division structure of World War II was retained and increased to above 19,000 officers and enlisted men. The U.S. Army fought the Korean War with the modified World War II infantry division structure.

In the early 1950s several Army planners thought a general war would be too costly to wage by conventional means because the Communist bloc could field more men and resources than the United States and its Allies. Firepower appeared to be the answer for overcoming the enemy. The Army, however, was hampered in its effort to understand the effects of tactical nuclear weapons because of the lack of data. Studies suggested that nuclear weapons could be used much like conventional artillery. To achieve increased firepower with decreased manpower, the Army created the "pentomic" division.

In the pentomic infantry division five small battle groups (headquarters and service company, five infantry companies, and one mortar battery each) replaced the three infantry regiments. Conventional and nuclear artillery, tank, signal, and engineer battalions, and a reconnaissance squadron with ground and air capabilities were added to the division. The division was also authorized trains, which included a transportation battalion, an aviation company, and an administration company. The transportation battalion was to have sufficient armored personnel carriers to move an entire battle group at one time. The aviation company, the first of its type, was to be placed in the trains for better supervision of its maintenance. The span of control was optimized in the division by giving each commander the maximum number of subordinate elements that could be controlled effectively. The pentomic division was authorized about 13,500 men of all ranks--a reduction of nearly 4,000 from the 1955 infantry division.

While the smaller battle groups were seen as more effective organizations to operate on a widely dispersed nuclear battlefield, there were other reasons for the Army's adoption of the new structure. The postwar defense budget concentrated on new weapons, aircraft, and ships rather than on soldiers. The Army's conventional rifles, machine guns, and trucks had little appeal. The pentomic division became a means by which the Army could stake a claim to a share of the nuclear arsenal. The pentomic division achieved that goal, but proved ill suited for the requirements of the conventional battlefield, given the communications technology of the late 1950s.

Although assigned nuclear weapons, the armored division did not adopt the pentagonal structure and instead served as the basis for the next divisional reorganization in the 1960s. Since World War II armored divisions had infantry, tanks, and artillery battalions, along with support units that could be organized into task forces. The ROAD organizations (Reorganization Objective Army Divisions) called for a division base consisting of a headquarters element; three brigade headquarters; a military police company; aviation, reconnaissance, engineer, and signal battalions; division artillery (105-mm. and 155-mm. howitzers, Honest John rockets, and 8-inch guns); a support command (headquarters; administration company; band; and medical, supply and transport, and maintenance battalions); and maneuver battalions (infantry and armor). Like combat commands in the armored division, the brigade headquarters had no permanently assigned units, but operationally controlled from two to five maneuver elements and support units as the tactical situation dictated. The unwieldly battle group was eliminated. Basic "building block" organizations were used to tailor task forces as required. To aid in organizing the task forces, units in the support command were designed so that their elements could be attached where needed.

Using flexible ROAD concepts, the Army has reorganized various types of divisions to meet opponents on real and potential battlefields. For the European theater, armored and mechanized infantry divisions were established. Infantry divisions were tailored for Korea and, later, for Vietnam. The airborne division was designed as a contingency force. The concept also accommodated the airmobile division, with its extensive use of helicopters for transport and tactical weapons platforms, and later the light division. With minimal adjustments to the ROAD base, by increasing and decreasing the number and types of maneuver battalions assigned to it, divisions achieved greater flexibility.

Both the devastation of the 1973 Arab-Israeli War and the Vietnam experience spurred Army thinkers to develop the AirLand Battle doctrine, which in turn introduced new weapons and technology into the divisions in the early 1980s. Without sacrificing the flexibility of the twenty-year-old ROAD concept, modern tanks, fighting vehicles, and field artillery weapons were assigned to the divisions. Building upon the airmobile concept and combat experience in Southeast Asia, more helicopters were introduced to the division. An aviation brigade was assigned to the division for command and control purposes. Under the "come-as-you-are, fight-as-you-are" approach to war, combat service support had to be immediately available in the battle area. Therefore, units in the division support command were reorganized to include three support battalions, one for each brigade to "arm, fuel, fix, and feed forward," and a main support battalion to provide additional logistical support and health services for the entire division. Each combat arms brigade headquarters also received a dedicated engineer battalion. Within divisions, the trend was to provide more specialized units, which could then be attached to the brigades to form combined arms task forces. Unit training, the formation of combined arms task forces, and their employment and sustainment in combat required the division to be structured, but flexible organization based on modular, interlocking building blocks. Commonality in doctrine, organizational procedures, and force design were essential for combined arms task forces.

In sum, the U.S. Army has had almost a century of experience in creating divisional organizations. Originally, time and distance as tactical factors determined division end strength. Later, concerns about strategic mobilization requirements dictated the size of divisional organizations. Combat organizations and the nature of a future enemy, especially the location of the next war, were especially influential considerations in the 1920s and 1930s. As a large standing Army emerged from the ruins of World War II, the existence of a known potential enemy led to divisional reorganizations, first the pentomic, and later the ROAD organizations.

Divisional organizations have fluctuated widely over the past century. It appears, with some variation, that the trend is toward smaller self-sustaining units. Sustainment was the reason for the huge square division of 1918, while mobility and the demands of a two-front war in vastly different terrain mandated the more mobile triangular division, which also fought independently, augmented by corps and army assets. The smaller pentomic division was an attempt at mobility and dispersal that overreached itself. Lacking appropriate technology (communications and air mobility), the division could perform neither function. The more flexible ROAD division has proved extremely adaptable, not only to changing battlegrounds, but to major advances in doctrine, technology, and weaponry. Indeed, its success now enables divisional brigades to operate independently on the battlefield.

Besides these considerations, technology and the changing nature of 20th century warfare have altered divisional structures. Technology, especially improved communications and weaponry, have enabled smaller units to execute missions previously thought suitable only for divisions. It may be no exaggeration to say today's infantry battalion is the equivalent in firepower of the World War II infantry division. Distance and space factors hold less meaning today, when structuring divisions, because flexible designs and improved technologies enable forces to be tailored to meet specific missions.

The trade-off, of course, is that highly trained, long-term professional soldiers are expensive to train and equip and heartbreaking to lose. When armies relied on brute force, true of armies until the 1980s, casualties, often in appalling numbers, might be considered the cost of doing business. That is no longer true, at least in the United States.

Finally, although small units now are capable of conducting sustained operations, these units require an overarching structure to give cohesion to their parts. Independent brigades, for example, might become much like the fabled Army regiments of the late nineteenth century: individually magnificent, but, as demonstrated in the Spanish-American War, incapable of operating together. Therefore, the division likely will remain the basic warfighting organization, but its structure and organization must continue to be reassessed in terms of future battlefield innovations, as well as with an eye on the lessons of the past.

Mr. John B. Wilson is a historian in the Center's Organizational History Branch of the Field Programs and Historical Services Division. He compiled the volume Armies, Corps, Divisions, and Separate Brigades in the Army Lineage Series, and currently is working with the Production Services Division on a forthcoming volume to be entitled "Divisions and Separate Brigades."