His background in guerrilla warfare led him in 1961, together with Walt Rostow, to push for the American armed forces and the State Department to emphasize counterguerrilla training. Hilsman was involved for more than two months in the U.S. responses to Soviet actions during the Cuban Missile Crisis of 1962, including developing informal communications with Soviet officials and the briefing of congressional leaders. He was also involved in the State Department's analysis of the Sino-Soviet split and the possible conditions for future warming in Sino-American relations.