“It wasn’t a chess game,” Landsman says after a moment. “On the board in Shpilman’s room. It was a problem. It seems obvious now, I should have seen it, the setup was so freaky. Somebody came to see Shpilman that night, and Shpilman posed him a problem. A tricky one.” He moves the pieces of the pocket chess set, his grasp of them sure, his hand steady. “White is all set up to promote his pawn, see. And he wants to promote it to a knight. That’s called underpromotion, because usually, you want to get yourself a queen. With a knight here, he has three different ways to mate, he thinks. But that’s a mistake, because it leaves Black — that was Mendel — with a way to drag the game out. If you’re White, you have to ignore the obvious thing. Just make a dull move with the bishop, here at c2. You don’t even notice it at first. But after you make it, every move Black has leads directly to a mate. He can’t move without finishing himself. He has no good moves.”
“No good moves,” Bina says.
“They call that Zugzwang,” Landsman says. “’Forced to move.’ It means Black would be better off if he could just pass.”
“But you aren’t allowed to pass, are you? You have to do something, don’t you?”
“Yes, you do,” Landsman says. “Even when you know it’s only going to lead to you getting check mated.”