It was about fighting a war to end the need for fighting any future wars; it was six wars ago.
Six years ago? It began 94 years ago. It was a war between Germany, the Austro-Hungarian Empire and the Ottoman Empire on one side and Imperial Russia, France, Britain and eventually the US on the other. It started when a Serb nationalist killed Archduke Ferdinand (Austro-Hungarian Empire) and Germany entered with some trepidation on the side of Austro-Hungary. Russia then came to the defense of their cultural ally, Serbia.
It is interesting that so many monarchs of the countries in question were related. I believe King George V, Czar Nicholas and the Kaiser were all related through Queen Victoria.