We have seen the standard queen sacrifice to create Boden’s mate. Here the route to the result is a little trickier. Again we see White’s dark-squared bishop with a clear path to b8, and a king that is trapped with no flight squares in the other direction; but to take advantage of this in Boden’s fashion White would need to move the b7 pawn and then follow up with his other bishop on a6. Notice the impediments to that pattern here: Black’s knight guards a6, and his pawn on b7 isn’t guarding anything White can take. But remember that a threat on a square guarded by a pawn can be as effective as a capture there. Thus White begins 1. Rc6+. Like a capture of a pawn on c6, this requires Black to play b7xR. The other problem still remains: the knight on b4 guards a6. So White makes use of a similar principle again, playing 2. Qxc6+—and this time requiring NxQ. Now Ba6 mates.

Black instead can make the first capture with his knight and the second with his b7 pawn; it doesn’t matter. The important point is to see how the two guards of a6 are drawn out of the way by successive threats—and sacrifices—on another square they both protect: c6.