The Russian Revolution of 1917, sparked by the hardships of World War I, led to the overthrow of the Tsarist regime and the establishment of the Soviet Union, the first communist state in the world.

The Treaty of Versailles, signed in 1919, was the main peace treaty that ended World War I. It imposed harsh conditions on Germany, including territorial losses, reparations payments, and disarmament.

The Ottoman Empire, which had been a major power for centuries, was dismantled after World War I. Its territories were divided among the Allied Powers, leading to the creation of new nation-states in the Middle East.

The League of Nations was created in 1919 as part of the Treaty of Versailles. It was the first international organization with the goal of maintaining peace and preventing future wars.

Italy gained significant territory, primarily from the Austro-Hungarian Empire, as a result of World War I. This included the regions of Trentino, South Tyrol, and Istria.

Nazism, a far-right political ideology, emerged in Germany after World War I. It was characterized by extreme nationalism, anti-Semitism, and a belief in the superiority of the Aryan race.

Russia experienced a civil war from 1917 to 1921, following the collapse of the Tsarist regime. The Bolsheviks, led by Vladimir Lenin, eventually emerged victorious and established the Soviet Union.

The Treaty of Brest-Litovsk, signed in 1918, ended the war between Russia and the Central Powers. It allowed Germany to gain control over vast territories in Eastern Europe.

All of the Central Powers experienced significant territorial losses as a result of World War I. Germany lost Alsace-Lorraine to France, Eupen-Malmédy to Belgium, and West Prussia, Posen, and Upper Silesia to Poland. Austria-Hungary lost territory to Italy, Romania, Czechoslovakia, and Yugoslavia. The Ottoman Empire lost territory to Greece, Armenia, and the Allied Powers.

The Treaty of Saint-Germain-en-Laye, signed in 1919, ended the war between Austria-Hungary and the Allied Powers. It resulted in the dissolution of the Austro-Hungarian Empire and the creation of new nation-states in Central and Eastern Europe.

The German colonies in Africa and the Pacific were divided among the Allied Powers after World War I. The United Kingdom gained control over Tanganyika, Cameroon, and Togoland. France gained control over French Togoland and Cameroon. The United States gained control over German Samoa and the Mariana Islands. Japan gained control over the Marshall Islands, the Caroline Islands, and the Palau Islands.

The Treaty of Neuilly-sur-Seine, signed in 1919, ended the war between Bulgaria and the Allied Powers. It resulted in Bulgaria losing territory to Greece, Romania, and Yugoslavia.

The United Kingdom gained control over the Ottoman Empire's territories in the Middle East, including Palestine, Transjordan, and Iraq, after World War I. France gained control over Syria and Lebanon.

The Treaty of Sèvres, signed in 1920, ended the war between the Ottoman Empire and the Allied Powers. It resulted in the Ottoman Empire losing vast territories, including most of its Arab provinces.