Introduction
Détente, meaning "relaxation of tensions," marked a period of eased relations between the USA and USSR from the late 1960s to the late 1970s. Both superpowers aimed to reduce the risk of nuclear war and foster cooperation. Initially, this resulted in successes like the Strategic Arms Limitation Talks (SALT) which limited the growth of nuclear arsenals. However, détente ultimately failed due to a complex interplay of misunderstandings, continued tensions, and internal pressures.

Misunderstandings and Differing Goals
The USA, under presidents Nixon and Ford, pursued détente with the belief that a more moderate USSR was emerging, willing to cooperate for mutual benefit. However, the USSR, led by Brezhnev, saw détente as an opportunity to buy time, seeking Western technology and trade to bolster its economy and military. Evidence of this can be seen in the continued Soviet military buildup throughout the 1970s, undermining the spirit of cooperation.

Continuing Tensions
Proxy wars, where the superpowers supported opposing sides in regional conflicts, fueled mistrust and undermined détente. The Vietnam War, where the USSR backed the North Vietnamese against the US-supported South, created a significant strain. Later, the Soviet invasion of Afghanistan in 1979, viewed by the US as a direct challenge to its interests, further escalated tensions. Ideologically, the fundamental divide between communism and capitalism remained a major obstacle, despite attempts at cooperation.

Soviet Assertiveness
Beyond Afghanistan, Soviet support for communist movements in Africa and Latin America, such as Angola and Nicaragua, directly challenged US interests and reignited Cold War fears. These actions, perceived as Soviet expansionism, contributed to the growing perception in the US that détente was a one-sided affair, benefiting the USSR while jeopardizing American security.

Internal Soviet Problems
The Soviet economy, plagued by inefficiency and stagnation, struggled to keep pace with the West. This economic weakness made maintaining détente difficult, as the USSR increasingly relied on Western technology and trade, potentially seen as a sign of weakness by the USA. This dependence fueled US skepticism about Soviet intentions and long-term commitment to peaceful coexistence.

Rise of Conservatism in the USA
The election of Ronald Reagan in 1980 marked a turning point. Reagan, a staunch anti-communist, viewed détente as a naive policy that empowered the USSR. His administration implemented a more assertive foreign policy, increasing military spending and challenging Soviet expansionism. These actions, coupled with Reagan's rhetoric labeling the USSR as an "evil empire," effectively ended détente and ushered in a new era of Cold War tensions.

Conclusion
The failure of détente was a result of a complex interplay of factors, including differing goals, continuing tensions fueled by proxy wars and ideological differences, Soviet assertiveness, internal Soviet economic problems, and the rise of conservatism in the USA. Ultimately, the inability to bridge the fundamental mistrust and ideological divide, coupled with conflicting geopolitical interests, made détente unsustainable. While détente did not achieve its ultimate goal of lasting peace, it laid the groundwork for future dialogue and ultimately contributed to the eventual end of the Cold War in 1991.