Eisenhower's commitment in South Vietnam was part of a broader program to contain China and the Soviet Union in East Asia. In 1954, the United States and seven other countries created the Southeast Asia Treaty Organization (SEATO), a defensive alliance dedicated to preventing the spread of Communism in Southeast Asia. In 1954, China began shelling tiny islands off the coast of Mainland China which were controlled by the Republic of China (ROC). The shelling nearly escalated to nuclear war as Eisenhower considered using nuclear weapons to prevent the invasion of Taiwan, the main island controlled by the ROC. The crisis ended when China ended the shelling and both sides agreed to diplomatic talks; a second crisis in 1958 would end in a similar fashion. During the first crisis, the United States and the ROC signed the Sino-American Mutual Defense Treaty, which committed the United States to the defense of Taiwan. The CIA also supported dissidents in the 1959 Tibetan uprising, but China crushed the uprising.