 The commander of the U.S. forces in Vietnam, Westmoreland, had decided with the support of McNamara to defend all of South Vietnam, believing that he could win via a strategy of attrition as he would simply inflict enough losses to destroy the enemy.The U.S. Army had sabotaged the efforts of Kennedy and McNamara to develop a more counterinsurgency role by simply declaring that the Army's basic unit, the division, was flexible enough to engage against guerrillas while also promising that the traditional fondness for using maximum firepower would not present a problem as firepower use would be "discriminating".In Vietnam, this led to divisions, whose size limited them and their supply trains to the road, using massive amounts of firepower against guerrillas who were often "nimble" enough to evade all of the firepower brought to bear.