Black Must have Played Which Move?

Originally posted by BigDoggProblem
Black must have played ...Ng3xRh1, though it does not matter which Knight takes the Rook.

Oops, Mephisto is right. I had the parity reversed from what it should be. Since white moved last, the parity of white and black must be different.

So the solution is that black played ...Nh3xRg1 at some point in the game.

Originally posted by Mephisto2
If black is to play, then knight moves alone cannot have done the job. The only solution for an odd number of moves for white is if black took the rook on g1 with a knight?

That is correct, Mephisto2.
Therefore he must have played N(h3)xR(g1).

(Oh, I didn't see your reply, Bigg Dogg.)