After the agreement that ended the Cuban Missile Crisis, relations between the two sides eased up. Several treaties, designed to reduce the number of nuclear weapons, were signed. In 1964, the USA under the Lyndon Johnson administration invaded North Vietnam, which resulted in a humiliating defeat for the USA and South Vietnam in 1975. During this period of Détente, the United States began building a good relationship with the People's Republic of China, a previous ally of the Soviet Union.