Why did world war 1 started and who caused it

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. ... At this point, Europe was at the brink of going to war.

Explanation:

World War 1 started when Archduke Franz Ferdinand of Austria was assassinated on June 28, 1914. This was the immediate cause but there were a series of events which triggered the war.

united states reinforcements contributed greatly to three allied victories in france at: cantigny (first major american battle), argonne (the largest in the united states military history, involving 1.2 million american soldiers), and château-thierry (one of the first actions under general pershing).