Why was the USSR suspicious of the west in the twentieth century?

The USSR was suspicious of the West in the twentieth century due to ideological differences, particularly the capitalist versus communist divide. The Bolshevik Revolution of 1917 instilled fears in Western powers of a spread of communism, leading to interventions and hostilities, such as the Allied intervention in the Russian Civil War. Additionally, the West's perceived encirclement and military alliances, like NATO, heightened Soviet paranoia about potential aggression. This mutual mistrust fueled the Cold War rivalry, marked by an arms race and geopolitical conflicts.