What caused WWI and who was to blame?

A: Alliance System
Because all of the great powers in Europe were allied with each other, it created a situation in which if one power attacked another, all the others would have to get involved in a war.

B: Colonial Rivalry
Colonial rivalry caused tension between the powers. For example, initially France and Britain argued a lot about their African colonies. Later, Germany created tension with Britain by supporting the Boer settlers in South Africa.

C: Naval Race
Germany believed to be a great empire it needed a large navy. It wanted a navy 2/3 the size of GB. However, Britain wanted to have a navy at least double the size of Germany's, so this created a naval race, and a lot of tensions between the countries.
D: Economic Rivalry
Germany's businessmen wanted to go to war with Briation because britain controlled about half of the tonnage of merchant ships.

E: Russia Supported Serbia
Made Russia more agressively anti-Austrian. Russia wanted to be the leader of the Slavs, and felt a responsibility to protect Serbia from A-H.
F: Germany Backing Austria at Crucial
Kaiser told A-H that Germany would give full support if A-H attacked Serbia. "Blank check"

G: Mobilization Plans
The Germans had a plan (Schlieffen Plan) to defeat France and Russia in one fell swoop. This plan does not leave any time for negotiation, and also involves a German of invasion of Belgiun (which violates Belgian neutrality, and forced GB into the war).

H: A "Tragedy of Miscalculation"
Various mistakes contributed to war:
-Austrians thought Russia would not support Serbia
-Germany gave Austria a blank check, forcing it into an uneccessary war.
-Politicians in Russia and Germany thought mobilization did not mean war
-Generals believed in a swift and decisize victory.