On June 28, 1914, the Austrian Archduke Franz Ferdinand was traveling in Sarajevo to inspect the Austria-Hungarian imperial armed forces there.
A Serbian nationalist threw a bomb at the roofless car the Archduke and his wife were traveling in.
The bomb rolled off the car before exploding, injuring bystanders.
Later in the day, the vehicle Franz Ferdinand was traveling in took a wrong turn, driving up right in front of other Serbian nationalists. One of them, 19 year old Gavril Princip, used the opportunity to assassinate the Archduke and his wife- firing at them from point blank range.
This assasination set off a chain of events that would start a World War between the two largest alliance systems in Europe.
World War 1 was the first major war that involved bombardment via aircraft. French leaders, worried about the potential devastation this could cause away from the front, built a "fake Paris" out of wood and electric lanterns just north of the real city.
At the height of the war, in the U.S., German street names were changed, and German language books were burned.
The Western Front was approximately 350 miles in length, but contained 25,000 miles of trenches.
British forces detonated approximately one million pounds of explosives under ground, beneath German soldiers at Messines Ridge, Belgium. The resulting blast was heard one hundred and fifty miles away in London.
On December 25, 1914, many British and German soldiers sang carols to each other, and many ventured out of their trenches and met opposing soldiers in "no man's land." It would be the last unofficial truce to take place.
In some areas of the western front, the soldiers exchanged gifts and souvenirs on Christmas eve, and on Christmas.
There were other unofficial truces leading up to this, with many soldiers wanting to "live and let live", and escape from the damp trenches, if only for a few hours.
Some accounts of the 1914 truce state that there were Christmas soccer matches between German and British soldiers.
The United States finally entered the war after the interception of the Zimmerman telegram. German foreign minister suggested to Mexico that should the United States declare war on Germany, it would be a great time for Mexico, with German assistance, to retake territory it had lost in the 1840s during the Mexican-American war.
"...we propose an alliance on the following basis with Mexico: That we shall make war together and together make peace. We shall give general financial support, and it is understood that Mexico is to reconquer the lost territory in New Mexico, Texas, and Arizona. The details are left to you for settlement..."