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Pentomic (cf.Greek pent(e)- and -tome, "of five parts") refers to a structure which included infantry and Airborne divisions adopted by the U.S. Army in 1957 in response to the perceived threat posed by tactical nuclear weapons use on the battlefield. The May 1957 issue of Army Information Digest notes that "Department of the Army studies have indicated that three types of [eventual Pentomic] divisions will continue to be required." Those are identified as: Airborne Division, Infantry Division, and Armored Division. Source: Article, "New Divisional Organization".[1]

"Pentomic Division" was "a public relations term designed to combine the concept of five subordinate units ('penta') with the idea of a division that could function on an atomic or nonatomic battlefield."[2]

From the Donald A. Carter 2015 book, Forging The Shield: The U.S. Army in Europe, 1951-1962,[3] "By 1958, the Army was ready to begin converting its divisions in Europe to the new pentomic organization. Its leaders had designed the new division specifically to operate on an atomic battlefield, and Europe was the theater where such a conflict was most likely to take place." (P. 299) "Although the [reorganization to pentomic was] to be servicewide, no command in the Army was in a better position to test the new concept than USAREUR [United States Army, Europe]. Its five combat divisions, three armored cavalry regiments, and heavy support structure made it the largest assemblage of fighting power in the service. Moreover, the pentomic structure and its accompanying atomic doctrine were specifically designed to deal with the Soviet Army. . . . Once the reorganizations were complete, USAREUR instructed the Seventh Army to evaluate the new pentomic infantry division and to recommend changes it deemed necessary to the unit's TOE. . . . [T]he Seventh Army put the new organization to the test. Beginning on 10 February [1958], [Exercise] SABRE HAWK fielded more than 125,000 soldiers for the largest maneuver yet in the history of the force. . . . In March, 1958, Seventh Army units down to division level participated in Command Post Exercise LION BLEU. . . . With two major exercises under its belt, the Seventh Army headquarters requested an evaluation of the new force structure and doctrine from its subordinate unit commanders. Initial comments reflected some uncertainty about tactics and techniques . . . [Combat unit commanders] pointed out that battle groups lacked any self-contained capability for rapid, cross-country movement. The division headquarters did have armored personnel carriers consolidated in its transportation battalion, but only enough to move one battle group at a time. For an organization whose battlefield survival depended on its ability to disperse widely when on the defense and then to concentrate its forces rapidly when preparing to attack, the shortfalls in communications and mobility were particularly troubling. [FN#20: ... Memo, Maj William F. Gunkel, Adj, for CG, 8th Inf Div, 4 Mar 1958 ...]" (pp. 301–306)

From page 111, The Cold War U.S. Army by Ingo Trauschweizer,[4] "The pentomic division [had been] designed as a five-year experiment in the field". Referring to the "three types of [eventual Pentomic] divisions [which] will continue to be required" (Airborne Division, Infantry Division, and Armored Division), page 17 of the May 1957 Army Information Digest, in the article, "New Divisional Organization", states in part, "Eventually, it is considered desirable that a single type [Pentomic] division be adopted".[5] That long term objective of the ultimate Pentomic division, namely a single type of division, is addressed on page 97 of Paul C. Jussel’s dissertation, “Intimidating the World: The United States Atomic Army, 1956-1960”:[6] “In the [Pentomic] divisions, every battle group was an integrated, mechanized combined arms team, ‘producing a unit that is no longer infantry, armored infantry, cavalry, or armor, per se, but a killer force that is compatible with the technological advances and needs of the immediate future.’ [EN#32] Thus the battle group could move or maneuver unlike any infantry battalion could. Because their vehicle was also intended to be a fighting vehicle, the battle group’s infantrymen had an advantage over the armored infantrymen who could not fight from his vehicle, but had to dismount to employ his weapons. Enemy tanks were countered with the mobile, protected anti-tank fires delivered by the battle group’s organic sections, thus obviating the need for the infantry regiment’s tank company.” From page 98: “Tanks would be completely removed from the [Pentomic] division and consolidated at corps level into tank brigades to be parceled out based on the battlefield needs. The [Pentomic] divisions, all armored and equipped with mobile anti-tank weapon systems, would not need the addition of tank units to perform its missions. Furthermore, the tank would not fit into the battle group or division design. Configured to be air-transported immediately to Europe and then to use air-mobility for movement and supply, the [Pentomic] division’s equipment had to be transportable on the C-123 and C-130 aircraft. The Army’s existing and proposed tanks were too heavy for this. So the CONARC planners removed them from the battle groups and designed corps operations to bring tanks into the area of operations by sea or rail at some future point.”

Beginning on page 108 of Jussel's above noted dissertation, the Pentana Study leading to the Pentomic reorganization is followed, to include, "As the Study gained exposure throughout the Army, students at both the War College and the Command and General Staff College . . . questioned both the organization and the concepts behind its employment. . . . Yet, as winter faded to spring 1956, the Army Staff was examining the details of the decision for future organizations. . . . [A]t the Army Staff level in early 1956, a decision [about the Pentana Study] was required . . . The Army Staff convened an ad hoc committee . . . The ad hoc committee recommended that the Pentana Study receive further study and war gaming but urged no significant reorganization until this was complete, technological improvements had been made, and all new equipment was in place.[EN#60] On 12 May 1956, the Army Staff's senior leadership assembled in a Pentagon room to receive a briefing on the optimum organization of the Army in the coming decade. They all listened carefully as the G3 briefer described the pentagonal organization, its strengths and weaknesses, and the Army staff's positions and recommendations. The briefer summarized the presentation with several requirements for CONARC [Continental Army Command] to meet before any further decisions could be taken on the Pentana Study. The general officers present then shifted to a discussion of the Army Staff's positions and recommendations, with the CONARC Commander arguing against the Army Staff. The argument centered on the value of the Pentana Study in the early part of the [1960-1970] decade. The Army Staff wanted revisions and further study to refine 'organizational and operational concepts for the 1960-70 period' before accepting the Pentana Study. The CONARC position acknowledged the requirement for further study, but accepted the Pentana Study as a benchmark . . . CONARC stood for immediate implementation while the Army Staff recommended further analysis. General [Maxwell D.] Taylor, in his role not only as Chief of Staff, but also as chief visionary for the Army, decided in CONARC's favor. He told the assembled Army Staff officers to 'avoid undue conservatism' and to 'be progressive in its thinking and approach to new ideas.' . . . The die had finally been cast: the Army would reorganize itself in line with the Pentana Study." (Jussel Dissertation, pp. 108-111)

From Chapter 4 “The Pentomic Era (1956-1960)” in Evolution and Endurance: The U.S. Army Division in the Twentieth Century by Richard W. Kedzior. (Santa Monica CA: RAND, 2000). The Pentomic division was intended to both survive a nuclear attack and successfully employ tactical nuclear weapons on the battlefield. This meant that the Army had to master these new weapons, and new doctrines and operational concepts for their employment, while attempting to minimize the effects of enemy nuclear weapons. U.S. Army formations, it was believed, would be required to mass quickly, strike, then disperse again to operate effectively and survive on the nuclear battlefield. New organizations and strategy emphasized three concepts: dispersion, flexibility, and mobility. American forces would disperse laterally and in depth, essentially scattered on the nonlinear battlefield. Units would avoid massing and thus refrain from presenting themselves as a strike-worthy target. Severe damage to one part of the division—even the command center—ostensibly would not prevent it from continuing the fight. Flexibility implied a more responsive command-and-control element, while mobility stressed the ability of forces to move rapidly and mass quickly from far-flung locations on the battlefield, thus requiring increased mechanization of the force.[EN#6] Five battle groups formed the fighting core of the Pentomic division, replacing regimental combat teams as the primary maneuver commands. The battle group was sized (at 1,427 total personnel, prior to 1959) to be large enough to fight independently, but small enough to be expendable. Subordinate units were similarly sized and organized to address the same dispersion and survival arguments. Each battle group was commanded by a colonel and had four (five after 1959) combat maneuver companies; each company in turn possessed five platoons. The battle group bolstered its firepower and sustainability through some organic support: it had a heavy mortar battery (4.2-inch), while its headquarters company had extensive reconnaissance, signal intelligence, maintenance, and medical assets. The battle group’s battlefield independence was, however, quite limited. It was clear that it still had to depend on the division for much of its combat and combat service support. Most indirect-fire support—in the form of Honest John (nuclear) rockets, and 105-mm, 155-mm, and 8-inch howitzers—came from division artillery, while armor support came from the division’s five tank companies. On the other hand, division artillery 105-mm howitzer batteries were so frequently attached to each battle group that they could be considered near-organic. Division engineer and tank companies were also similarly assigned. Division trains possessed all armored personnel carriers (tracked) and large wheeled vehicles, and the fact that there was only enough of them to move one battle group at a time severely hampered the division’s mobility. Only the Army’s infantry and airborne divisions were reorganized to the Pentomic design; troop strength in each fell to about 13,500 and 11,500, respectively. Armored divisions retained the World War II–type combat command structure, with the exception that an Honest John rocket battery was added to each for nuclear capability.[EN#7] The Pentomic era was a strategically muddled and dark period in Army history. The Pentomic division was conceived, developed, and presented as proof that the Army was adapting to the nuclear age with dramatic, modern results. In its attempt to market itself to regain relevance in the nation’s security planning, the Army dangerously lost its focus, leading to rushed force designs and incomplete testing and wargaming throughout the Pentomic division’s development. Although it was admittedly planned and adopted to be merely a transitional design—filling the gap until technology or an improved design would arise—the Pentomic division encountered more problems than most decisionmakers expected. From the start, Army leaders utterly failed to comprehend the damage that tactical nuclear weapons would do to the battlefield and battlefield operations, leaving the Pentomic organization unable to fulfill wishful predictions of Army performance on the nuclear battlefield. Severe equipment and technical shortcomings also ensured that the Pentomic division was simply not prepared to succeed in conventional warfare, either. The battalion-size battle groups did not possess sustainable combat power, while shortcomings in mobility and logistical assets also left the division ineffective. The division did not possess enough vehicles to fulfill the Pentomic doctrinal concepts of timely massing and dispersion of forces. In addition, the lack of intermediate command echelons and inadequate communications technology created significant command and control problems for commanders at all echelons. In the end, Pentomic division organization was unwieldy and unmanageable and proved to be less than robust vis-à-vis task organizing to suit specific missions. [EN#8] The dual atomic-conventional role imposed on the Pentomic division designers was impossible to fill. At the most fundamental level, there was an inherent contradiction in the objectives and doctrine of an “atomic battlefield” force and a conventional force. The preferred atomic force would consist of small, highly mobile reconnaissance elements designed to find suitable targets and force the enemy into kill zones, while conventional forces would be designed with elements capable of seizing and holding ground. The resultant Pentomic force—intended to satisfy the requirements of both missions—could not do either.[EN#9] . . . 6 A. J. Bacevich, The Pentomic Era: The U.S. Army Between Korea and Vietnam (Washington, D.C.: National Defense University Press, 1986), p. 65; and Hawkins, Glen R., United States Army Force Structure and Force Design Initiatives, 1939-1989, Washington, D.C.: U.S. Army Center of Military History, 1989, p. 23. 7.Hawkins, pp. 26–32. 8 Staff Officers Field Manual: Organization, Technical, and Logistical Data, U.S. Army Field Manual 101-10 (Washington, D.C.: Department of the Army, 1959), pp. 32–35; Bacevich, pp. 133–135. 9 John J. Midgely, Jr., Deadly Illusions: Army Policy for the Nuclear Battlefield (Boulder, CO: Westview Press, 1986); pp. 72–79.


The infantry and Airborne division structures commonly known as Pentomic divisions are actually two related organizations, officially known as Reorganization of the Airborne Division (ROTAD) and Reorganization of the Current Infantry Division (ROCID). The Pentomic structure was a reaction to the perceived threat of Atomic weapons on the modern battlefield and a chance for the Army to secure additional funding.

Previously the US Army had fought World War I with the "square" organisation, each division having two brigades, each with two infantry regiments. Prior to American participation in the Second World War the organization was changed to "triangular" with each division directly controlling three regiments, and eliminating the brigade echelon from the division.

1960 Pentomic Infantry Division. The five "Battle Groups" on the left of the diagram dominate the Divisional structure

The ROTAD was implemented first, with the 101st Airborne Division reorganizing under test tables of organization published on 10 August 1956. The core of the division was five infantry battle groups, each containing five infantry companies, a headquarters and service company, and a mortar battery. A headquarters and headquarters battalion contained a headquarters and service company, an administration company, an aviation company and a reconnaissance troop. The division artillery contained a headquarters and headquarters battery, five 105mm howitzer firing batteries, and an Honest John missile battery. A support group contained a headquarters and service company, a maintenance battalion, a quartermaster parachute company, a supply and transportation company, and a medical company. Separate signal and engineer battalions completed the organization, which required a total of 11,486 men. After a series of tests by the 101st Airborne Division, the Continental Army Command (CONARC) approved slightly modified tables of organization, and all three airborne divisions (the 11th, 82nd and 101st) were reorganized during 1957.[7][8]

Shortly after the 101st began testing ROTAD, the CONARC began developing ROCID, forwarding the initial ROCID tables of organization to the Army Staff on 15 October 1956. The core of this initial ROCID organization, similar to ROTAD, consisted of five battle groups, each with a headquarters and service company, a mortar battery and four infantry rifle companies. The Division Artillery was organized with a 105mm howitzer battalion, with five firing batteries, and a composite battalion with four firing batteries: two 155mm howitzer batteries, an 8in howitzer battery and an Honest John missile battery. In addition to a headquarters and headquarters company, a tank battalion, reconnaissance squadron, engineer battalion, signal battalion and division trains completed the division’s organization. The division trains consisted of a headquarters and headquarters detachment (which included the division’s band), an ordnance maintenance battalion, a medical battalion, a transportation battalion, a quartermaster company, an aviation company and an administrative company. The Army’s nine infantry divisions completed reorganization into the new structure in 1957.[9][10][11][12]

The standard infantry division was seen as being too clumsy in its fixed organization. Units were organized in a system of "5's". A division was organized with five battle groups, each commanded by a colonel. Each battle group consisted of five line (rifle) companies, a mortar (4.2 in) battery, and a headquarters company with signal, assault gun and recon platoons. Each company was commanded by a captain. The Division Artillery was initially organized with a 105mm howitzer battalion, with five batteries, and a composite battalion with four firing batteries: two 155mm howitzer batteries, an 8in howitzer battery and an Honest John missile battery. Later, the Division Artillery was re-organized into five direct support battalions (each with one 105mm firing battery and one 155mm firing battery), and a general support battalion (with the 8in firing battery and the Honest John battery). Two of the direct support battalions were equipped with self-propelled howitzers, and three were equipped with towed howitzers. In order to man the increased number of batteries, the 4.2in mortar batteries in each battle group were removed.[13] The 1961 addition of "Davy Crockett" recoilless spigot guns with atomic warheads supplemented the concept of the atomic age army. Figure 2, "The Pentomic Division", on page 107 of Bacevich's book "The Pentomic Era" shows a graphic from the "Annual Report of the Secretary of Defense for Fiscal Year 1956" depicting the initial ROCID organization. The graphic shows "5 Combat Groups of 5 Companies Each"; 5 105mm Mortar Batteries; an Honest John Rocket Battery; 5 105mm Howitzer Batteries; and, 5 HQ & Service Companies, with each including "Reconnaissance, Signal, Supply, & Medical".[14]

The pentomic division very closely resembled the wartime 82nd and 101st Airborne Divisions which had each fought with five parachute or glider infantry regiments. Their regiments were smaller and more austere than the regular infantry regiments of the infantry divisions. This was no accident as the top leaders of the army at this time were all airborne Generals—Ridgway, Taylor, and Gavin. The armored divisions were not affected as their three combat commands were considered appropriate for the nuclear battlefield.


In July 1955 General Taylor became the Chief of Staff of the United States Army where he selected General William Westmoreland as his Secretary to the General Staff. Westmoreland recalled that Taylor was told by President Dwight Eisenhower he had to do something to give the Army "charisma"; something in Westmoreland's words to give the Army a "modern look".[this quote needs a citation] In the mid-1950s the Army was facing a loss of morale following the end of the Korean War when the lion's share of government funding and publicity was going to the nuclear-armed United States Air Force and Navy. After Taylor designed the Pentomic concept, he promoted Westmoreland to what was then the youngest major general in the US Army to command Taylor's former wartime command, the recently reactivated 101st Airborne Division, that would be the first unit to be reconfigured in the Pentomic structure.[15]

American army officers felt the plan was "ill started, ill fated and hopefully short lived" with some thinking it was a scheme of Taylor's to increase the number of active divisions in the army when he had actually cut their combat manpower.[16]

Westmoreland recalled that as the Pentomic structure with all its flaws was a creature of the Chief of Staff, any officer who valued his career was loath to be heard to criticize it.[17] Westmoreland also briefed all officers in the division "Our job is not to determine whether it will work-our job is to make it work". Following the end of Westmoreland's command of the 101st in 1960 he recommended the Pentomic structure be abolished.[18]


When the U.S. Army division was reorganized under the Pentomic structure in 1957, the traditional regimental organization employed by the Army was to be eliminated. This raised questions as to what the new units were to be called, how they were to be numbered, and what their relationship to former organizations was to be. Many of the Army's senior officers were determined to perpetuate the historic lineages of the Army, unlike the situation after the Civil War when the Grand Army of the Republic persuaded Congress to forbid the linkage between the Civil War era Union Army Corps and the new Corps organized for the Spanish–American War.

On 24 January 1957 the Secretary of the Army approved the CARS concept, as devised by the Deputy Chief of Staff for Personnel, which was designed to provide a flexible regimental structure that would permit perpetuation of unit history and tradition in the new tactical organization of divisions, without restricting the organizational trends of the future.[19]

Separate brigades were organized with two or three battle groups. The 2nd Infantry Brigade was organized as follows:[20]

  • Headquarters & Headquarters Company
  • 1st Battle Group, 4th Infantry
  • 2nd Battle Group, 60th Infantry
  • 3rd Battalion, 4th Artillery
  • 1st Battalion, 76th Artillery
  • Troop F, 5th Cavalry
  • Company F, 34th Armor
  • Company G, 34th Armor
  • Brigade Trains
  • 232nd Engineer Company (Combat)
  • 712th Engineer Company (Combat)


The Pentomic systems was found to be flawed in several ways.

  • Training: Officers would command with long periods of time between assignments to maneuver units. This would erode the experience and competence of Battle Group commanders once the experienced officers of World War II and Korea retired.
  • Span of control: Most people are capable of managing 2–5 separate elements. The pentomic battle group contained seven companies and in combat would habitually have 2–4 more attached such as engineers, artillery, or armor.
  • Loss of regimental cohesion: Traditional infantry regiments had long histories and commanded strong loyalty from their assigned soldiers. The Battle Groups, and later, the ROAD brigades, combined infantry battalions from different regiments in a chaotic fashion that eliminated regimental cohesion.
  • Loss of a level of command: Previously there had been Company Commanders (Captain), Battalion Commanders (Major or Lieutenant Colonel), and Regimental Commanders (Colonel); the Pentomic structure eliminated the level of Battalion Commander.[19]

End of ROCID

In December 1960, the Army began studying proposals to reorganize again that was hastened by newly elected President John F. Kennedy's "Doctrine of Flexible Response". This led to the ROAD (Reorganization Objective Army Division) initiative by 1963.

Other nations

The Australian Army implemented a similar structure, called the Pentropic organisation, between 1960 and 1965 but reverted to its previous structure after experiencing difficulties similar to those experienced by the U.S. Army.

The New Zealand Army planned to reorganize its forces around a derivative of the Australian concept, but the Australians abandoned the concept before the New Zealanders could start the change.[21]

The Turkish Army utilised the pentomic structure in 1960s for a period before adopting the American ROAD divisional organisation.[22]

The West German Army attempted reorganization around the pentomic structure in 1957, abandoning the idea in a few years.[23]

After the signature of the Pact of Madrid with the United States, the Spanish Army abandoned the organization inherited from the Spanish Civil War to adopt the pentomic structure. Three experimental pentomic infantry divisions were created in 1958, followed by five additional ones in 1960. The pentomic structure was abandoned in 1965, when the Spanish Army adopted the French doctrine and organization of the era.[24]

See also


  1. Army Information Digest ("The Official U. S. Army Magazine"), May 1957, pp. 16-23.
  2. Johnathan M. House, Toward Combined Arms Warfare: A Survey of 20th-Century Tactics, Doctrine, and Organization, 1984. United States Army Combat Studies Institute. US Army Command and General Staff College. Fort Leavenworth, Kansas. p. 155.
  3. Washington D.C.: United States Army Center for Military History.
  4. University Press of Kansas, 2008.
  5. Cameron Station, Alexandria VA: Army Information Digest, USGPO.
  7. Directory and Station List of the United States Army, 15 August 1957
  8. Wilson, John B. Maneuver and Firepower: The Evolution of Divisions and Separate Brigades (CMH Pub 60-14-1). Army Lineage Series. Washington: Center of Military History: 272-276.
  9. McKenney, Janice E. The Organizational History of Field Artillery, 1775–2003 (CMH Pub 60-16). Army Lineage Series. Washington: Center of Military History, 2007: 250-252.
  10. Directory and Station List of the United States Army, 18 February 1957
  11. Directory and Station List of the United States Army, 15 August 1957
  12. Directory and Station List of the United States Army, 17 February 1958
  13. McKenney, Janice E. The Organizational History of Field Artillery, 1775–2003 (CMH Pub 60-16). Army Lineage Series. Washington: Center of Military History, 2007: 250-252.
  14. "The Pentomic Era". 1986. Retrieved 5 March 2011.<templatestyles src="Module:Citation/CS1/styles.css"></templatestyles>
  15. pp. 44–46 Sorley, Lewis Westmoreland: The General Who Lost Vietnam Houghton Mifflin Harcourt, 11/10/2011
  16. p.178 Linn, Brian McAllister The Echo of Battle: The Army's Way of War Harvard University Press, 30 June 2009
  17. Lewis, Adrian R. The American Culture of War: A History of US Military Force from World War II to Operation Enduring Freedom Routledge, 11/01/2013
  18. p.75 Mrozek, Donald J. Air Power and the Ground War in Vietnam The Minerva Group, Inc., 01/06/2002
  19. 19.0 19.1 "The Pentomic Era". June 1952. Retrieved 5 March 2011.<templatestyles src="Module:Citation/CS1/styles.css"></templatestyles>
  20. Directory and Station List of the United States Army, 15 August 1960
  21. Damien Marc Fenton, 'A False Sense of Security,' Centre for Strategic Studies:New Zealand, 1998, appendix
  22. British Military Attache's Annual Report on the Turkish Army, Annex A to DA/48, dated 30 March 1974, FCO 9/2127 via Public Record Office, Kew
  23. "West Germany: The Pentomic Army". Time. June 1957. Retrieved 5 March 2011.<templatestyles src="Module:Citation/CS1/styles.css"></templatestyles>
  24. PUELL DE LA VILLA, Fernando (2010). "El devenir del Ejército de Tierra (1945-1975)". In Fernando Puell de la Vega y Sonia Alda Mejías (ed.). Los Ejércitos del franquismo. Madrid: IUGM-UNED. 2010. Pp. 63-96.

External links