The Cold War was a conflict between the United States of America and the Union of Soviet Socialist Republics from the aftermath of the Second World War to the end of the 20th century. It was so named because the two superpowers conducted their conflict through proxy wars rather than direct confrontation, owing to fears over the likelihood of mutually assured destruction should the two ever initiate large-scale warfare.
The period of tension between the two countries spawned out of a mutual distrust at the end of World War II. The United States remained concerned that the USSR was pursuing a expansionist policy and seeking to spread its Marxist-Leninist political ideology. On the flip side, the Soviet Union bore just as much disdain for the United States' steadfast commitment to capitalism. With such high tension existing between the geopolitical superpowers, the two nations remained on high alert for imminent war throughout the era. All the while, they competed one another in other areas, engaging in what became known as the Space Race and nuclear arms race.
In the 1940s and 50s, widespread American dread over communism led to an event known as the Red Scare, whereby thousands of Americans were targeted as communists without the presence of proper evidence. The witch-hunts were fueled by the American public's prevailing suspicions of communist spies lurking among them and were galvanized by the senator Joseph McCarthy. Because of his role in instigating the Red Scare, it, alongside its characteristic disregard for proper investigation, became commonly known as McCarthyism.
This era was therefore marked by an ever-pervading anxiety over the next world war that seemed to loom over the horizon. However, despite the longevity of the conflict, the actions of leaders such as President Richard Nixon managed to stave off full-scale war. With easing tensions and the dissolution of the Soviet Union, the conflict came to a close in 1991 without the widely anticipated great war ever erupting.