I'm currently a few books into Harry Turtledove's 'War that Came Early' series and I don't understand how a WWII that started over Czechoslovakia could have possibly caused a chain reaction that would lead the Nazis to seek an alliance with the UK and France in order to fight the Soviets better. I read the first book in the series a while back so I might have forgotten something, but I'm not sure. Could a WWII that started over Czechoslovakia have conceivably led to an alliance between these three powers against the Soviets? If so, why would it happen in that reality, but not ours?