[untenured]

Now had Hitler not invaded Russia, that could have been an entirely different story.

I don't think he could have not invaded Russia. The need to destroy "Jewish Bolshevism" (and "Jewish Anglo-American capitalism," for that matter) was integral to his worldview.

[driftless2]

"could not have invaded"

You are correct. Everything I've read about Hitler not only stresses his habit of taking huge risks but also his desire to conquer. He made this clear in Mein Kampf. Once he acquired the reins of power, the future was determined. Churchill saw this, but few others did.