In Step 3 of the German attack, if the formation on the Allied Command card does not match the formation of the Allied unit that I'm attacking, do I discard that card?
Surely discarding is what one does with a card after drawing it like this, as a general convention in games, isn't it? There are various other places in the game where the rules tell you to draw a card and possibly do stuff with them, without explicitly telling you to discard them afterward.
Granted, it would be best to explicitly say so, but I can't seriously imagine you're not meant to discard it.
Or do I shuffle it back into the deck?
Is there some place in the rulebook that would suggest doing this?
Or does it even matter since the German Command cards are what drive the turn length?
It would matter in terms of future Allied draws. I expect that the intent was not to see the same allied card again until the deck is depleted and reshuffled.