第二次世界大戰結束後，美國與蘇聯因意識型態的對立，雙方陣營形成國際冷戰的 局勢。美國於戰後針對蘇聯集團採取圍堵政策，以防止共產勢力於全球擴張而危及美國 國家利益。 1949年，國民政府遷臺。美國為避免中共加入蘇聯陣營，不願軍事援華，而對中華 民國的前途採取袖手旁觀的立場。 1950 年6 月韓戰爆發後，杜魯門（Harry S. Truman, 1884-1972）宣布中立臺海，避 免海峽兩岸另起衝突而危及美國西太平洋防線安全。為迫使中共同意韓戰停火，美國新 任統艾森豪（Dwight D. Eisenhower, 1890-1969）於1953 年3 月聲明解除中立臺海。韓 戰後，中共成為美國在遠東地區的冷戰強敵。 杜魯門政府於韓戰期間為牽制中共武力，開始協助中華民國軍隊針對中國大陸沿海 島嶼進行突襲行動。中共為貫徹解放臺灣的目標並阻止中美雙方簽訂共同防禦條約，於 1954 年對金門發動九三炮戰，引發臺海一次危機。艾森豪政府以中華民國政府同意聯合 國安理會停火案為條件，完成簽訂〈中美共同防禦條約〉宣示協防臺澎，扭轉了杜魯門 時代袖手旁觀的對華政策。 ;After World War II, the world was divided into two camps due to the ideological antagonism between the United States (the U.S.) and the Soviet Union, and the Cold War began. The U.S. started to implement the policy of containment toward the Soviet Union bloc to prevent the expansion of communism from jeopardizing the U.S. national interests. In 1949, the Nationalist Government relocated to Taiwan. To keep the Chinese Communist Party from joining the Soviet Union bloc, the U.S. did not provide Taiwan with military aid at the time, taking a hands-off position on the future of the Republic of China (the R.O.C.). In June of 1950, the Korean War broke out. The U.S. President Harry S. Truman (1884-1972) declared the neutralization of Taiwan Strait to avoid any armed hostilities in the strait to secure the safety of the U.S. defense line in the Western Pacific. In March of 1953, to force the People’s Republic of China (the P.R.C.) to concur on the armistice agreement of the Korean War, Truman’s successor Dwight D. Eisenhower (1890-1969) issued a statement to lift the neutralization of Taiwan Strait. After the Korean War, the P.R.C. became a great power rival hostile to the United States in the Far East during the Cold War. The Truman government had been assisting the R.O.C. military to raid against the P.R.C. along the coast of mainland China to concentrate the P.R.C. force on the Korean Peninsula during the Korean War. To achieve its end of liberating Taiwan as well as to obstruct the signing of Mutual Defense Treaty between the R.O.C. and the U.S., the P.R.C. bombarded Kinmen on September 3, 1954, setting off the First Taiwan Strait Crisis. On condition that the R.O.C. government concurred on the truce negotiation of the United Nations Security Council, the Eisenhower government eventually signed the Mutual Defense Treaty with the R.O.C., declaring to assist in defending Taiwan and the Pescadores. Thus the U.S. hands-off policy toward the R.O.C. set by the Truman government was foundamentally changed.
