When Mao Zedong's Red Army swept Chiang Kai-shek's nationalist-ruled Republic of China off the mainland in 1949, Chiang's armies retreated to a chain of offshore islands that stretched from the coast of Zhejiang to Hainan Island. The Matsu Islands were soon transformed from a sleepy archipelago of no political significance to a major flashpoint of the Cold War. During the Cold War, Matsu was nothing but a hardship post dreaded by Taiwanese soldiers. Separated from the mainland by only nine miles at its closest point, it was close enough for nationalist and communist gunners to lob shells at one another on alternating days of the week. The Matsu Island group was once extremely strategic for the nationalists. As some of the only territory Taiwan controlled outside the island of Taiwan, it was key to preserving the fiction that the Republic of China ruled over the entire mainland.