 The Pentomic structure was a reaction to the perceived threat of nuclear weapons on the modern battlefield and a chance for the Army to secure additional funding.Earlier 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 WWII the organization was changed to "triangular" with each division directly controlling three regiments and eliminating the brigade echelon from the division.