Besides the points mentioned above, Germany had also lost more than 2 million men in the war, and was also suffering from poverty, etc., as her economy had been severely crippled, if not destroyed, by the war. Forced to give up ALL her colonies, disarmament and extreme reparations had only increased the impact on Germany and her citizens. To a certain extent all these were not very fair to Germany.
The colonies were a source of national pride for most German citizens. Besides, Germany saw the TOV as merely another excuse by the victors to annex her overseas territory - they were originally for the newly set up League of Nations to rule but were given to the Allied nations to govern due to the League's lack of resources.
As for disarmament, the Rhineland that separates France from Germany became a demilitarized zone, meaning that no German soldiers were allowed in there. The army was limited to 100,000 men, very small for a nation Germany's size, and the German Navy was only allowed to keep six battleships. Besides all this, the German armed forces were not allowed to build or buy any armed vehicles, submarines, or military aircraft. What was unfair to Germany in this was that NONE of the other countries disarmed, or were forced to disarm, to the extent that Germany was.
Worst of all was the reparations Germany had to give the Allied countries (6,600 million British pounds). Such a staggering amount left her with no means whatsoever of staging a post-war economic recovery, and was notably many times the value of the damaged she had caused. Hence Germany believed that the reparations
were intentionally meant to cripple her and keep her weak.
All these had only intensified Germany's motivation for future revenge. Besides the fact that Germany was not even invited to the Paris Peace Conference to appeal the decision, Adolf Hitler in the 1930s had promised to tear up TOV if he was elected, and when he did, he properly kept to his promise. World War Two started...