It was scheduled for June 28, 1914 for Franz Ferdinand, Austrian Archduke, to inspect the troops. He had planned to meet his wife at the station and then go to the City Hall for dinner.
Death of Franz Ferdinand
The terrorist group, The Black Hand had decided that the Archduke should be assassinated. They were trained in bomb throwing and marksmanship. They were stationed along the route that the Archduke would be taking from the city hall to the inspection.
United States Join the War
The first two terrorists were unable to throw their grenades because of the crowded streets. The third had thrown his which landed under the car. Although the Archduke and his wife, Sophia, were unharmed, some of his attendants were severely injured and hospitalized.
Germans weren't very happy about imperialism.
On the way to the inspection, the driver had realized that he had taken a wrong turn. So he stopped and began to go in reverse. As he was going in reverse one of the terrorists named Gavrilo Princip fired two shots. The first hit the pregnant Sophia in the stomach, she died almost instantly. The second shot hit the Archduke in the neck. He died a short while later.
On May 7, 1915, a German submarine torpedoed the passenger liner, Lusitania. Nearly 1200 civilians lost their lives. The U.S was fired up about this so they joined the war.
Germany was tired of other countries taking over land. So, Germany allied with other countries. This is on of the reasons that the war started.