The Cold War primarily began due to significant ideological differences between the United States and the Soviet Union following World War II. The United States, a capitalist nation, promoted liberal democratic principles, individual freedoms, and a market-driven economy. On the other hand, the Soviet Union embraced Communism, advocating for a collectivist society, state control over the economy, and a centralized government. These opposing ideologies and economic systems led to tensions and mutual distrust.