The origins of the Second World War are generally viewed as being traced back to the First World War (1914-1918). In that war Germany under the ultra-nationalistic Kaiser Wilhelm II along with its allies, had been defeated by a combination of the United Kingdom, United States, France, Russia and others.
The war was directly blamed by the victors on the miltant nationalism of the Kaiser's Germany; it was Germany that effectively started the war with an attack on France through Belgium.
France, which had suffered a previous defeat at the hands of Prussia (a state that merged one year later with others to form Germany) in the Franco-Prussian War in 1870, demanded revenge for its financial devastation during the First World War (and its humiliation in the earlier war) ensured that the various peace treaties, specifically the Treaty of Versailles imposed tough financial reparations and restrictions on Germany.