Pentomic refers to a structure for infantry 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 official name of this structure was ROCID- Reorganization of the Current Infantry Division. However, it was generally known as the Pentomic Division. 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. 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 5 "Battle Groups", each commanded by a colonel. Each Battle Group consisted of five line (rifle) companies, a combat support company, and a Headquarters & Headquarters company. Each company was commanded by a captain. Artillery units were organized with 5 batteries- 4 were howitzers, the fifth was a mortar battery. The addition of "Davy Crockett" rockets with atomic warheads brought the Army into the atomic age.

The Pentomic Division very closely resembled the wartime 82nd and 101st Airborne Divisions which had each fought with 5 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.

Lineages & Honors

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 January 24, 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.

Separate Brigade were organized with 2 or 3 battle groups. The 2nd Infantry Brigade was organized as follows:

  • Headquarters & Headquarters Company
  • 1st Battle Group, 4th Infantry
  • 2nd Battle Group, 60th Infantry
  • 1st Battalion, 76th Artillery
  • Company F, 34th Armor
  • Company G, 34th Armor
  • Brigade Trains
  • ??th Engineer Company
  • ??th Engineer Company
  • Troop F, 5th Cavalry


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 7 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.

End of ROCID

In December 1960, the Army began studying proposals to reorganize again. This led to the ROAD (Reorganization Objective Army Division) initiative by 1963. 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.

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