10. The Fall of the Soviet Union (1991)
In December 1991, the collapse of the Soviet Union unfolded with stunning speed, dissolving a superpower that had dominated world affairs for decades. Overnight, the political map of Europe changed, and the Cold War era abruptly ended. Few regime changes in history have matched the magnitude and rapidity of this seismic shift. As History.com notes, the fall of the USSR set off waves of transformation, independence movements, and new alliances, profoundly influencing global politics for years to come.
