Treaty of Versailles: After World War I, the Treaty of Versailles was imposed on Germany, which resulted in significant territorial changes. Germany lost Alsace-Lorraine to France, Eupen-Malmédy to Belgium, North Schleswig to Denmark, and West Prussia, Posen, and Upper Silesia to Poland. The treaty also mandated Germany to cede control of Danzig (now Gdańsk) to the League of Nations as a Free City. These territorial losses had a profound impact on Germany's borders and contributed to the rise of nationalist sentiments in the country.
Rise of Fascism and Expansionist Policies: The interwar period saw the rise of fascist regimes in several European countries, most notably Italy under Benito Mussolini and Germany under Adolf Hitler. Both leaders pursued aggressive expansionist policies that led to significant changes in the map of Europe. Mussolini's Italy invaded Ethiopia in 1935 and later annexed Albania in 1939. Hitler's Germany, driven by its desire for Lebensraum (living space), began a series of territorial annexations and military conquests.
German Territorial Expansion: Germany's territorial expansion began with the reoccupation of the Rhineland in 1936, which was in violation of the Treaty of Versailles. In 1938, Germany annexed Austria through the Anschluss and incorporated the Sudetenland region of Czechoslovakia following the Munich Agreement. In March 1939, Germany seized the remainder of Czechoslovakia and established the Protectorate of Bohemia and Moravia.
Invasion of Poland and Start of World War II: On September 1, 1939, Germany invaded Poland, which marked the beginning of World War II. The subsequent German conquests and occupations led to further significant changes in the map of Europe. Poland was divided between Germany and the Soviet Union, with the latter annexing eastern territories that were predominantly inhabited by Ukrainians and Belarusians.
Soviet Expansion: The Soviet Union also pursued territorial expansion during this period. In addition to its annexation of eastern Poland, the Soviet Union invaded and annexed the Baltic states of Estonia, Latvia, and Lithuania in 1940. It also annexed Bessarabia and Northern Bukovina from Romania in the same year.
Post-World War II Changes: Following the defeat of Germany and its allies in World War II, the map of Europe underwent further significant changes. Germany lost additional territories, including East Prussia, Silesia, and Pomerania, which were transferred to Poland. The Allies also established new borders for countries such as Czechoslovakia, Hungary, Romania, and Yugoslavia. The Iron Curtain divided Europe into Eastern Bloc countries under Soviet influence and Western Bloc countries aligned with the United States.
In summary, the map of Europe changed significantly from World War I to World War II due to a combination of factors including the Treaty of Versailles, the rise of fascism and expansionist policies, German territorial expansion, Soviet expansion, and the aftermath of World War II. These changes reshaped the political and geographic landscape of Europe and laid the foundation for the Cold War era that followed.