During the Cold War, which lasted from the late 1940s to the early 1990s, espionage became a crucial tool for both the United States and the Soviet Union. Each side sought to gather intelligence on military capabilities, political strategies, and technological advancements of the other. This often involved spies, surveillance, and covert operations to gain an advantage in the ongoing ideological conflict. Notable espionage activities included the use of spy satellites, wiretapping, and the recruitment of double agents. High-profile cases, such as the Cambridge Five in the UK, highlighted the extent of infiltration by Soviet spies within Western governments. These efforts significantly influenced international relations during this tense period.