World war 1
it was made bigger/worse by

In world War 1, the assassination of Archduke Franz Ferdinand in Sarajevo on 28th June 1914, it triggered a chain of events that resulted in World War 1. After the assassination, Austria-Hungary threatened war on Serbia.

Explanation:

World War I began in 1914 after the assassination of Archduke Franz Ferdinand and lasted until 1918. During the conflict, Germany, Austria-Hungary, Bulgaria and the Ottoman Empire (the Central Powers) fought against Great Britain, France, Russia, Italy, Romania, Japan and the United States (the Allied Powers) After four years of combat and the deaths of some 8.5 million soldiers as a result of battle wounds or disease, the Allies were victorious. Although World War I began in 1914, the United States did not join the war until 1917. The impact of the United States joining the war was significant. The additional firepower, resources, and soldiers of the U.S. helped to tip the balance of the war in favor of the Allies.