World War I lasted more than four horrific years and took the lives of 8.5 million people. So why did soldiers spontaneously put down their guns and shake hands? And why did they start fighting again? See more »

World War I was the great armed conflict of 191418. Until World War II, it was often called the Great War because it was the most destructive and widespread war the world had ever seen. See more »

The use of aircraft in warfare led to great changes in intelligence gathering and tactics. See more »

To sustain huge armies in the field, each nation had to wage total war that is, commit all resources to the war effort. See more »

Invasion of Belgium. On July 27 Belgium and Luxembourg were informed by Germany of its intention to pass through. See more »

The Western Front. In November, 1914, Moltke was relieved of his duties as supreme commander and in December was replaced by General Erich von Falkenhayn. See more »

Two great battles were fought on the Western Front in 1916—at Verdun (February 21-July 11) and the Somme (July 1-November 18). See more »

In early 1917 the United States was finally pushed into the war. On January 31, Germany resumed unrestricted submarine warfare, in an attempt to halt the imports of food and supplies into Britain. See more »

At the beginning of 1918 the peoples of Europe were weary of war. Among the Central Powers, Austria-Hungary, Bulgaria, and Turkey were near collapse. See more »

As early as August, 1918, senior German commanders suspected that their forces would collapse in the face of a sustained Allied offensive. See more »