Final answer:
The relationship between the United States and the Soviet Union after World War II is best described as the Cold War, characterized by ideological conflict, indirect military engagements, technological competition, and proxy wars, without direct military confrontation between the two nations.
Step-by-step explanation:
The Cold War After World War II
The relationship between the United States and the Soviet Union after World War II can be categorically defined as the Cold War, a period marked by intense rivalry and a bipolar world. Although the two superpowers were allied during the war, their cooperation quickly dissolved into mutual suspicion. Each country was convinced of the superiority of its own social and economic system and sought global influence. Although called 'cold' because it did not manifest in direct military conflict, the tension translated into an arms race, propaganda battles, and proxy wars that took place in other nations. The so-called Cold War was a conflict driven by two opposing economic and political ideologies: democracy and capitalism versus communism.
Both nations exerted their influence on other states through a variety of means such as espionage, political maneuvers, and indirect military engagements. The Cold War also spurred advancements in technology and scientific research, exemplified by the space race and the concept of Mutually Assured Destruction (M.A.D.) as a deterrent to nuclear warfare. This period was characterized by a series of proxy wars like those in Vietnam and Afghanistan, where the superpowers supported opposing sides.