The three factors that I think that lead to World War I was German Ship Law, Balkan Crisis, and the Bosnian Crisis. They are all quite closely related still there is a level of influence in each one of these factors.
The German Naval Law in 1900 literally marked the beginning of trouble. The Kaiser said he wanted a navy because he wanted colonies in Africa. In 1906 he started to build dreadnoughts. Because of this the British felt threatened. The reason was that the sea way was very important for the British because their colonies are all over the place. They need to control the seas in order to have control over the colonies that they had. If Germans start building a Navy, there is a really big possibility that the Germans will block British's income of resources and control of the sea. This cause the Germany and Britain to had a little navy race, just like how the Cold War worked, instead of seeing who had more Atomic Bombs this was between Germans and British seeing who had more dreadnoughts.
By 1912 British navy was far bigger than Germans. This means British already have enough power to beat the Germans. This could have cause the Germans to be frustrated because they need the sea to get to Africa. This caused hate between British and the Germans.
The Bosnian Crisis in 1908 is probably more important than the German Naval Law. That was because the Naval Law of 1900 only caused hatred, but the Bosnian Crisis actually made Russia incredibly mad and made them made a vow that can lead to war. What happened in the Bosnian Crisis in 1908 was that there was a rebellion in Turkey, because of this the Austrian - Hungarians decided to...