 Out of a major review of the military challenges confronting the U.S. initiated by McNamara in 1961 came a decision to increase the nation's "limited warfare" capabilities.These moves were significant because McNamara was abandoning President Dwight D. Eisenhower's policy of massive retaliation in favor of a flexible response strategy that relied on increased U.S. capacity to conduct limited, non-nuclear warfare.The Kennedy administration placed particular emphasis on improving the ability to counter communist "wars of national liberation", in which the enemy avoided head-on military confrontation and resorted to political subversion and guerrilla tactics.