The terms on which World War I ended set the stage for World War II, which began just 20 years later, by negatively impacting the belligerent countries politically, economically and socially. The Treaty of Versailles, which formally ended World War I in 1919, was an instrument of vengeance against the Central Powers, and dissatisfaction over its terms left the defeated nations vulnerable to extremist movements promising revenge.
Germany was dealt with especially harshly. The country, which had only been unified 50 years earlier, was forced to cede over 10 percent of its home territory and all of its overseas possessions. Germany was required to take full responsibility for World War I and agreed to pay crushing reparations that the fragile domestic economy couldn't hope to sustain. Militarist Germans were further insulted by the extreme restrictions on the size and composition of the post-war German army and navy.
Politically, the former German Empire was in chaos. The Kaiser's 1918 abdication left a power vacuum that extremist parties rushed to fill. By 1931, the largest political party in Germany was the Communists, with the extremist Nazi Party a close second. Dictatorship, militarism, a sense of grievance and severe economic hardship eventually made the Nazis' message of redemption attractive enough to set Europe back on the road to war.