Franz Ferdinand, Archduke of Austria, was assassinated on June 28, 1914. Ferdinand was the nephew of Emperor Franz Joseph I and heir to the Austrian throne.

The Schlieffen Plan (named after its author, Alfred Graf von Schlieffen) was Germany's strategic blueprint for the beginning of World War I. The Germans, however, encountered unexpected resistance as they marched through Belgium to attack France from the North. This delay allowed British and French forces to mobilize sufficiently to halt the German advance on Paris at the First Battle of the Marne in September, 1914.

On Christmas Day, 1914, German and British troops called a temporary truce and serenaded each other with Christmas carols from their opposing trenches. There were even a few calls for visits across the "No Man's Land" and small gifts such as whisky and cigars were exchanged. When British commanders learned of the impromptu cease-fire they were enraged and vowed that the "Christmas Truce" would not be repeated in following years.

On January 16, 1917, Germany dispatched the Zimmerman Telegram to Heinrich von Eckardt, the German ambassador to Mexico. The telegram, however, was intercepted by the British, and although the American public initially believed it to be a forgery, its authenticity was eventually proven and the resulting outrage hastened the U.S. entry into the war.

Originally conceived by Lt. Col. Ernest Swinton in 1914 and developed under the encouragement of Winston Churchill, the first tank, the Mark I, debuted at the Battle of the Somme on September 15, 1916. Although the commanding officer was criticized for spreading the tanks out along the front line instead of using them in a tight formation, the British did move their front line forward about 2,500 yards on that first day. They did not, however, break through the German line as they had hoped.

With approximately 1.8 Million total fatalities, Germany lost the the most lives during World War I. The Soviet Union was next with approximately 1.7 Million total fatalities, followed by France with approximately 1.385 Million total fatalities.

Franz Ferdinand and his wife were killed in Sarajevo by Gavrilo Princip, a sickly 19-year-old just finishing high school, a member of Young Bosnia and one of a group of assassins organized and armed by the Black Hand.

Although best known from its usage for American troops in the First World War, the term "doughboy" as applied to the infantry of the U.S. Army first appears in accounts of the Mexican-American War of 1846-48.

Phosgene is the chemical compound with the formula COCl₂. This colorless gas gained infamy as a chemical weapon during World War I where it was responsible for about 85% of the 100,000 deaths caused by chemical weapons.

Known by the stage name Mata Hari, Margaretha Zelle was a Dutch exotic dancer and courtesan who was convicted of being a spy for Germany and executed by firing squad in France on October 15, 1917. Mata Hari, which means "Eye of the Dawn" died at dawn.