One of the deadliest wars in history, it lasted from 1914 to 1918 and involved more than 20 countries on six continents. It pitted the Central Powers of Germany, Austria-Hungary and Turkey against Britain, France, Russia, the United States and other Allied powers. It was the first truly global conflict and was unprecedented in its scope and scale of slaughter and destruction.

Known as the Great War, it had a profound impact on the world that lasted well beyond its conclusion. It created the League of Nations, which was intended to thwart future conflicts. It also resulted in the collapse of the German, Russian and Austro-Hungarian Empires and the end of the Ottoman Empire. Over 65 million people died, including an estimated 15 million civilians who were killed by strategic bombing, man-made famine and genocide.

The United States entered the war on April 6, 1917, after it intercepts the Zimmermann Telegram, in which German Foreign Minister Arthur Zimmermann offers Mexican President Emiliano Zapata land for the surrender of Texas, New Mexico and Arizona. The war was stalemated in the Western Front (Battle of the Marne) and on the Gallipoli peninsula. It was halted in the summer of 1915 on the Western Front by the French and British redeploying around Paris, and in March and April on the Gallipoli peninsula, where Turkish sea and land forces were defeated.

The U.S. Navy placed a massive barrage of sea mines off the coast of Germany, creating a 300-mile barrier that sank many U-Boats and forced German submarine crews to waste time trying to avoid them. The United States pushed for the Versailles Peace Conference that imposed heavy war reparations on Germany and established the League of Nations. It was resentment of the terms of the treaty that fueled Adolf Hitler’s rise to power in Germany, which ultimately led to World War II.