It started with the attack on Pearl Harbor in Hawaii
http://50thingstonotknow.blogspot.com/2006/12/world-war-iii-almost-started-in-1995.html
In simplest terms, the main cause of World War two was World War one, consult your local history teacher for more information.
The UN was started in 1945, just after World War II.
It was the assasination of archduke franz Ferdinand that directly started world war 1
It started when ............................................ was assasinated
It was Germany's invasion of Poland that began World War II.
World War One started.
The assassination of Archduke Ferdinand
The assassination of Franz Ferdinand
World War I started in 1914, when a Bosnian terrorist shot Franz Ferdinand, who was a Duke from Austria-Hungary. Austria-Hungary declared war on Bosnia, which caused a lot of other countries to declare war on each other. Eventually, the whole world was involved.
Which war? After WWII the Cold War started and caused a division of democracy vs. communism.