Final answer:
The deterioration in relations between the US and Soviet Union post-World War II was due to ideological conflicts, espionage events like the U-2 incident, and mutual perceptions of the other as aggressive and expansionist. The global superpowers engaged in proxy wars, competing for technological superiority and vying for influence across the world in what came to be known as the Cold War.
Step-by-step explanation:
Causes of the Breakdown in Soviet-US Relations
After World War II, the relationship between the United States and the Soviet Union deteriorated due to ideological differences, geopolitical strategies, and mutual suspicion. Initially, both nations worked together to defeat Axis powers, but after the war, they emerged as competing superpowers with opposing visions for global order. The US, advocating for democratic governance and capitalist economics, was pitted against the Soviet Union's communism underpinned by state control and a planned economy.
The 1950s saw increased tensions, exemplified by the 1960 U-2 incident where a US spy plane was shot down over Soviet territory. This event symbolized the lack of trust and the prevalence of espionage between the two nations. Moreover, the ideological crusade against communism within the US, such as McCarthyism, and the Soviet Union's suppression of democracy and human rights abuses, fueled hostilities. Foreign policy approaches, like the expansive doctrine of NSC-68, depicted the Soviet Union as a substantial and relentless threat, raising the stakes of the conflict.
Global supremacy battles spanned various arenas, including proxy wars like the Vietnam War and the Afghan conflict, and the race for technological and space exploration dominance. The Cold War was marked by the constant threat of escalation into nuclear war, a standoff which promoted a sustained period of rivalry without direct military confrontation between the US and the Soviet Union.