The escalating tensions between China and Taiwan.

The status of Taiwan is among the biggest flashpoints in U.S.-China relations, which are at their lowest point in decades. Though the United States does not have official relations with Taiwan, it is the island’s most important international backer. The roots of the Taiwan issue go back almost 75 years to 1949, when the ruling Nationalist Party was defeated by Mao Zedong’s Communist Party in the Chinese Civil War. The U.S. has a longstanding policy of “strategic ambiguity” on how it would respond if China invaded Taiwan, the idea being to deter China from invading and discourage Taiwan from doing something that might provoke a Chinese military response.