The Double Tenth Agreement signed on 10 October 1945 is the only legal document between the two parties. The following , was engulfed by Cold War history and the American foreign policy of containment in East Asia after the Korean War. Before the Korean War broke out, the US was preparing for a coup d'état in mid-1950 to replace Chiang Kai-shek with Hu Shih and Sun Li-jen and neutralize the ROC's legal status under UN Trusteeship to block any legal claim of the PRC on Taiwan, as proposed by United States Department of State official Dean Rusk. The Formosa Resolution of 1955 was passed unanimously by the United States Congress. Resolving the cross-Strait relationship required both sides to rethink definitions of basic concepts such as sovereignty, "one China" and unification.