What led to the end to detente?

The end of détente, the easing of Cold War tensions between the U.S. and the Soviet Union, was primarily influenced by several factors, including the Soviet invasion of Afghanistan in December 1979, which heightened U.S. fears of Soviet expansionism. Additionally, the rise of more aggressive U.S. foreign policies under President Reagan, who viewed the USSR as an "evil empire," further escalated hostilities. The arms race resumed, and both sides increased their military expenditures, leading to a breakdown in diplomatic relations and a return to a more confrontational stance.