The WWII was caused by the dominant tendencies of Germany with support of Japan and Italy who methodically destroyed the peace agreement of international relations established by the Peace of Versailles.
Explanation:
These tendencies had economic and social backgrounds leading to expansion by imposing their totalitarian system and dictatorship of ‘superhumans’ and depriving other nations of their freedom and independence.
Germany’s tendencies were mostly to reclaim what was taken away from it in 1919 and to overpower the Europe, creating a military and economic power being able to rule the world.
Japan wanted to rule Britain, US and Netherlands out of the Far East and Asia (with its great colonial possessions and economic influence and to master himself "with his part of the world"; Italy joined because of ideological closeness and foreign policy clashes with Britain and wanted to rule the Mediterranean and Balkan region.
