What marked the end of the Cold War?

The end of the Cold War is most significantly marked by the dissolution of the Soviet Union in 1991. This event represented the final collapse of the communist regime that had been the primary rival to the Western capitalist nations, particularly the United States, throughout the Cold War era. The Soviet Union's disintegration resulted in the independence of multiple former Soviet republics and a significant shift in the global political landscape, leading to the end of decades of ideological confrontation.

While the fall of the Berlin Wall is a critical event that symbolized the decline of communist influence in Eastern Europe, it was the dissolution of the Soviet Union that fundamentally concluded the Cold War by dismantling the core of the communist bloc. Other options, such as the establishment of NATO and the signing of the Treaty of Versailles, are significant historical events but are not directly related to the Cold War's conclusion. NATO was created in 1949 as a military alliance against the Soviet threat, and the Treaty of Versailles was signed in 1919, long before the Cold War even began. Thus, the dissolution of the Soviet Union represents the definitive end of the prolonged conflict between the two superpower blocs.