Which event refroze the thaw in the cold war?

The event that refroze the thaw in the Cold War was the Soviet invasion of Afghanistan in December 1979. This aggressive action ended the period of détente, as it heightened tensions between the United States and the Soviet Union. In response, the U.S. increased its military spending, supported anti-Soviet forces in Afghanistan, and boycotted the 1980 Moscow Olympics, marking a significant escalation in Cold War hostilities.