If Hitler simply wanted to kill all Jews, why did he wait until the onset of WWII to put them in concentration camps? WWII began in 1939. Hitler came to power in 1933. Why didn't he round them up and send them away between those years?

Answer: As a result of the back-stabbing, treason, and treachery of organized, radical Jewry within Germany during WWI (a memory fresh in every German's mind), Hitler sought to remove this perceived threat to Germany's security by placing them in concentration camps DURING WAR TIME (I forgot to add).

America did the same thing with Japanese Americans during WWII -- we removed a perceived threat to our security from society, and put them in concentration camps. The difference was, the Japanese Americans hadn't done anything in the past to warrant such fear by the government.

Sign above concentration camp: "Arbeit Macht Frei" = "Work Sets You Free".