How did World War II begin? It’s not the simplest of questions, nor does it have the easiest answer. However, America in the 20th Century: World War II: The Road to War has a good overview – use the EdPuzzle below (make sure you sign in).
Want more? Take a look at “Did WWI Lead to WWII?” from the History Channel below.
You can also check out this AMAZING interactive of World War II from my good friends at the American Battle Monuments Commission (seriously, I met the External Affairs head, and he is super cool).