Who lead the countries to war in world war 1?

They made Germany take the blame because Germany was the most aggressive, although Serbia had really started it by assassinating the new Austria-Hungarian King. This was followed up by Russia warning Austria that if they attacked Serbia, Russia would attack Austria-Hungary. A-H called Germany to support them if Russia helped, then Russia called French for support. When French realized they would lose, they called Great Britain who didn't really want to join, but joined in. Later on in the war, Austria-Hungary left the war, leaving Germany on it's own. Soon, Great Britain, France and Russia began losing vs Germany and Italy who joined Great Britain later on as Germany began losing when America joined