tangent squared: invading Russia

I heard recently that not only did far more of the German high command agree with this beforehand than would admit to it afterwards, but that it nearly succeeded. A getaway train was prepared and waiting for Stalin at Moscow station, and if he had turned up and escaped on it, Russia would have fallen. Connoisseurs of pivotal moments might like to add this one to their collection. Anyone know anything more about it? Spectacled Bear.