After a long history of failed pacification programs, the successes reported for CORDS in the 1968–1972 period were partially attributable to the heavy casualties the Viet Cong suffered during the Tet Offensive and subsequent actions in 1968. The number of Viet Cong guerrillas is estimated to have been reduced from 77,000 in 1968 before Tet to 25,000 in 1972 and the Viet Cong infrastructure from 84,000 to 56,000. However, although the number of battalion-size battles declined, the number of small unit actions by the Viet Cong nearly doubled during the same time period, illustrating the impact of hearts and minds (as believed by its advocates). In January 1972 Ambassador Bunker warned that the communists would have to "mount a major military offensive...to prove his public claims that Vietnamization and pacification are failures." True to Bunker's prediction, on March 30, 1972, North Vietnam launched its Easter Offensive. Although South Vietnam, with American air support, withstood the offensive, the North Vietnamese army gained control over sizable areas of South Vietnamese territory and displaced more than one million people.