Clemenceau was so hostile to the Germans because he felt that Germany was a major threat to France. He wanted this threat to be ended, which is why he took such a hostile approach to Germany in the treaty. The major reason for this was the fact that Germany had invaded France twice in the previous 50 years. Germany had defeated France in 1871 and had come very close to defeating France again in World War I. Clemenceau was afraid that Germany might try again. This was why he wanted Germany treated so harshly in the Treaty of Versailles.