The US-Taiwan Mutual Defence Treaty, or USA/Republic of China Mutual Defence Treaty was a defensive pact signed in December 1954. It was signed by the US to increase stability in the strait, both by precluding a Communist invasion, and by discouraging Chiang Kai-shek from instigating military escalation. The treaty omitted the islands of Kinmen and Matsu from the territories under ROC jurisdiction the US is compelled to protect in case of an invasion.
The treaty was unilaterally abrogated in 1979 by the Carter administration.