On June 28th, 1914, Archduke Franz Ferdinand was assassinated. He was killed by a Serbian sympathizer. This event made Germany go to war on Serbia. These events set off a chain reaction of thing leading to the first World War
In 1915 a British liner named the Lusitania was sunk by a german u-boat. The Lusitania had many Americans on board. A swaying factor in the war. This was a swaying factor because America Was swayed into entering the war. America is a world power and can easily help either side.
The Zimmerman Telegram was a encoded message from Germany to Mexico. The telegram was asking Mexico to enlist in the war. In return Texas, Arizona, and New Mexico would be given to mexico. Britain had intercepted the coded message and let America know. Another major deciding factor in America and WW1.