The most famous use of trench warfare was the Western Front in World War I. It has become a byword for stalemate, attrition, sieges and futility in conflict.

With 26 aerial victories, Eddie Rickenbacker was the United States' most successful WWI fighter pilot. He was also a race car driver and automotive designer.

The Treaty of Versailles ended the state of war between Germany and the Allied Powers. It was signed on 28 June 1919, exactly five years after the assassination of Archduke Franz Ferdinand.

The Germans were the first to use flamethrowers in WWI. Their flamethrowers could fire jets of flame as far as 130 feet.

The French 75mm cannon, accurate up to 4 miles, developed a reputation among their German opponents as the "Devil Gun". French military commanders claimed that its Devil Gun won the war.

There were approximately 9 Million fatalities during World War I. However, there were also approximately 23 Million wounded or missing, bringing the total number of casualties to about 32 Million. Russia suffered the most casualties with approximately 6.7 Million either dead or wounded. These statistics reflect only military casualties as there are no reliable figures on civilian casualties during World War I.

On 28 July, 1914, one month after the assassination of Archduke Franz Ferdinand, Austria-Hungary declared war on Serbia.

Japan was an important member of the Allied Powers, formally declaring war on Germany on 23 August 1914.

Spain remained neutral throughout World War I.

Edith Cavell was celebrated for saving the lives of soldiers from both sides without discrimination, but when she helped some 200 Allied soldiers escape from German-occupied Belgium during the First World War, she was arrested, accused of treason, found guilty by a court-martial and sentenced to death. Despite international pressure for mercy, she was shot by a German firing squad.