History of the Republic of China its remaining islands in Fujian as vital for any future campaign to defeat the PRC and retake mainland China. On 3 September 1954, the First Taiwan Strait Crisis began when the PLA started shelling Quemoy and threatened to take the Dachen Islands. On 20 January 1955, the PLA took nearby Yijiangshan Island, with the entire ROC garrison of 720 troops killed or wounded defending the island. On January 24 of the same year, the United States Congress passed the Formosa Resolution authorizing the President to defend the ROC's offshore islands. The First Taiwan Straits crisis ended in March 1955 when
History of the Republic of China operations of 1950 were more successful: they led to the Communist conquest of Hainan Island in April 1950, capture of Wanshan Islands off the Guangdong coast (May–August 1950) and of Zhoushan Island off Zhejiang (May 1950). In June 1949 the ROC declared a "closure" of all mainland China ports and its navy attempted to intercept all foreign ships. The closure covered from a point north of the mouth of the Min River in Fujian province to the mouth of the Liao River in Manchuria. Since mainland China's railroad network was underdeveloped, north-south trade depended heavily on sea lanes. ROC naval