He became the General Secretary in 1960, officially becoming the main personality in the party after Hồ Chí Minh. After Hồ's death, Lê Duẩn took over the leadership of North Vietnam. Throughout the Vietnam War of 1955 to 1975, Lê Duẩn took an aggressive posture, seeing attack as the key to victory. When South Vietnam was reunited with North Vietnam in 1976 and the party was restructured, Lê Duẩn became General Secretary of the Party. Lê Duẩn and his associates were overly optimistic about the future. The Second Five-Year Plan (1976–1980) failed and left the Vietnamese economy in crisis. He endorsed the Vietnamese invasion of Cambodia of December 1978, aiming to overthrow the Chinese-backed Khmer Rouge regime. This had a serious impact on relations between Vietnam and China, with Vietnam responding with the deportation of ethnic Chinese and China carrying out a heavy-loss punitive expedition against Vietnam in 1979. From then on, Vietnam maintained a closer alliance with the Soviet Union and joined Comecon in 1978.