The Triple Entente was a political and military alliance between France, Russia, and Great Britain, formed in response to the Triple Alliance.

The Triple Alliance was a political and military alliance between Germany, Austria-Hungary, and Italy, formed in 1882.

The assassination of Archduke Franz Ferdinand of Austria, heir to the throne of Austria-Hungary, on June 28, 1914, was the immediate cause of World War I.

Austria-Hungary declared war on Serbia on July 28, 1914, after Serbia refused to accept an ultimatum demanding that it suppress anti-Austrian propaganda and allow Austrian officials to investigate the assassination of Archduke Franz Ferdinand.

The United States declared war on Germany on April 6, 1917, after Germany resumed unrestricted submarine warfare in the Atlantic Ocean.

The Battle of Amiens, which took place from August 8 to 11, 1918, is considered the turning point of World War I. The Allied forces, led by the British, launched a massive offensive against the German lines, breaking through and forcing the Germans to retreat.

Russia suffered the most casualties in World War I, with an estimated 1.7 million soldiers killed and 4.9 million wounded.

Serbia had the highest percentage of its population killed in World War I, with an estimated 12.5% of its population killed.

The Treaty of Versailles was the peace treaty that ended World War I. It was signed on June 28, 1919, between the Allied Powers and Germany.

The Treaty of Versailles required Germany to give up territory to the Allied Powers, pay reparations to the Allied Powers, and was forbidden from having a military.

The League of Nations was an international organization established after World War I to promote peace. It was founded on January 10, 1920, and headquartered in Geneva, Switzerland.

The main goals of the League of Nations were to prevent war, resolve international disputes peacefully, promote disarmament, and improve the lives of people around the world.

The League of Nations failed because it was unable to prevent World War II, resolve the Manchurian Crisis, and stop the rise of Adolf Hitler.

World War I led to the collapse of the Russian Empire, the rise of the United States as a global power, and the creation of new nation-states in Europe.

An estimated 17 million people died in World War I.