With two Knights the Checkmate cannot be forced. For let the Black King be driven into a corner, the task of forcing the Checkmate still fails.
This is a critical position. In order to achieve the Checkmate the King must be driven into the corner. Therefore, its escape, KB1 must he cut off. If to this end X from K5 to Q7 and Black replies K-R1, the Black King will return to X1, because that square must not now be cut off by either X to B6 or X from Q5 to K7 on account of the law of Stalemate. Returning, the King will again threaten to escape via B1 and thus keep one of the Knights busy such as the one on Q7. And no further progress can be achieved. Only a manifest blunder will enable White to bring about the Checkmate, namely, by
1. X-B6ch. K-R1.
Obviously, this move is a grave mistake, for thus Black voluntarily goes where White wants to drive it; the move K-B1 would Draw.
2. X-B7Mate.