The other reason that causes World War I is Franco-Prussian War. The war was a conflict between the Second French Empire and the Kingdom of Prussia. Prussia wanted to unify Germany Empire and started to expend its power in Europe. On the other hand, the Second French Empire restored its power in Europe and Prussia became a barrier of France. However, the north German and south German joined together and defeated the Second French Empire. As a result, French lost land on the north of French and paid for German 5 billion francs. This increased the conflict between European countries and lead to the War World I.