In checkless chess it’s illegal to give check without giving checkmate. This changes the whole complexion of the game. T.R. Dawson published this example in Die Welt in 1951. White is to mate in two moves.

The answer, 1. f6, threatens 2. Qf5, which strangely is mate because the black king can’t move off the long light diagonal, since that would discover check by the black bishop without giving checkmate. Black can try to prevent this finish by playing 1. … Qc8, guarding f5 and thus making 1. Qf5 itself illegal. But this permits 2. Nxd6, which now is mate because the black king has nowhere to run on the long diagonal and 2. … cxd6 is illegal because this would give a mateless check.

Similarly, if Black tries to stop 1. Qf5# with 1. … Qxf6, then 2. Nc5 is mate because Black can’t capture the knight — again, this would expose White’s king to an illegal check. And if Black tries to answer White’s first move with 1. … d5, to block the long light diagonal and free his king to flee elsewhere, then White can play 2. Qe5#, an ordinary (and legal) mate.