Both Voldemort and Hitler were halfbloods. Voldemort had a Muggle father and a witch as a mother, making him a halfblood, while Hitler was actually partially Jewish. Also, Voldemort and Hitler both wanted everyone to be “pureblood”, to Hitler this meant blonde-haired, blue-eyed, pale-skinned Germans. To Voldemort this meant wizards without a single trace of Muggle blood in their veins. Hitler had the Nazis, & Voldy had the Death Eaters. Together they tried to commit mass genocide, for Hitler the Jews, for Voldemort the Mudbloods. They killed at lot of people with “non-pure blood”, but never actually succeeded in wiping out an entire race. And finally, one last reason why Harry Potter is like World War Two is that the people who officially ended the wars were both named Harry (Harry S. Truman and Harry J. Potter).
Harry Potter and the Deathly Hallows Part 2