The Central Powers consisted of Germany, Austria-Hungary, the Ottoman Empire, and Bulgaria.

The Allied Powers consisted of France, United Kingdom, Russian Empire, Italy, and Japan.

The assassination of Archduke Franz Ferdinand was the immediate trigger, but the underlying causes were the rise of nationalism and imperialism, and the arms race among European powers.

World War I began on July 28, 1914, with the declaration of war by Austria-Hungary on Serbia.

World War I ended on November 11, 1918, with the signing of an armistice between the Allies and Germany.

Russia suffered the most casualties during World War I, with an estimated 1.7 million soldiers killed.

The United Kingdom had the most powerful navy during World War I, with a fleet of over 2,000 ships.

Germany had the most powerful army during World War I, with a force of over 4 million soldiers.

The Treaty of Versailles was the peace treaty that ended World War I, signed on June 28, 1919.

The Treaty of Versailles required Germany to lose territory to the Allied Powers, pay reparations, and disarm.

World War I led to the collapse of the Ottoman Empire, the Russian Revolution, and the rise of fascism in Europe.

It is estimated that over 16 million people died in World War I.

The Battle of the Marne was the first battle of World War I, fought from September 5 to 12, 1914.

The Battle of Meuse-Argonne was the last battle of World War I, fought from September 26 to November 11, 1918.

John J. Pershing was the American general who led the American Expeditionary Force in World War I.