The event in the 20th century that drastically changed French politics was World War II. The wartime occupation of France by Nazi Germany from 1940 to 1944 led to significant political and social upheaval. Following the Liberation of France in 1944, there was a push for political reform and the establishment of the Fourth Republic, replacing the Vichy regime. The war also fostered a strong sense of nationalism and prompted the decolonization process in French territories. These changes laid the groundwork for the Fifth Republic in 1958, which established a more stable government under Charles de Gaulle, marking a new chapter in French political history.