The Americans joined the war because of the German policy of unrestricted submarine warfare, where that any ships that were in British waters would be drowned without warning. Also, Germany contacted Mexico and told them that if they allied with Germany, they would help them regain the land they lost to the US. That was the last straw, and the US joined the war
Archduke Franz Ferdinand were going to visit Sarajevo, the caapitol of Bosnia. The Black had was a secret society committed to ridding Bosnia of Austrian rule, and one of the members of the Black Hand, assassinated Ferdinand. Because the assassination was by a Serbian, Austia decided to use the murder as an excuse to punish Serbia. Serbia offered to have several issues settled vy an international conference. Austria, did not want to negotiate, and on 1914, Austia declared war on Serbia
The Nationalist Party's first great leader was Sun Yixian. In 1911, the forerunner of the Nationalist Party succeeded in overthrowing the last emperor of the Qing dynasty.