1. The "war guilt" clause. Germany was forced to accept responsibility for causing the Great War, and was required to pay reparations to the Allies.
2. Germany had to give up large portions of its territory and lost colonial territories.
3. The German military had major restrictions imposed on it -- it had to be a volunteer military only, of no more than 100,000 men, and they could not have an air force.
4. The League of Nations was created as an international organization to pursue peaceful resolutions to conflicts.