What if Hitler died in 1940 after the fall of France?
Maybe he choked on some French food, or had a heart attack or some other illness, or maybe he overdosed on one of the many drugs he was on. Just as long as it wasn't assasination or suicide.
Who would take over after his death? How would this new leader continue the war or attempt peace? Would this new leader be insane enough to attack the Soviet Union, or would he try to keep peace with them as long as possible?