Pentomic

Pentomic (cf.Greek pent(e)- and -tome, "of five parts") refers to a structure for 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.

"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."

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.

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.

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