Lesson
Black to move. Main line: 26... Ng3+ 27. hxg3 hxg3+ 28. Nh3 Bxh3 29. gxh3 Rxh3+ 30. Kg2 Rh2#
26...Ng3+! forces 27.hxg3 and drags the h-pawn off the file. Black immediately replaces it with 27...hxg3+, opening the rook’s route from h8.
The bishop removes the remaining knight on h3. After the forced pawn recapture, ...Rxh3+ and ...Rh2# complete the chase.
This is a clearance sacrifice in its purest form: the sacrificed piece matters less than the line it opens for the piece behind it.
Every move in the sequence is forced, which is what makes a piece sacrifice calculable rather than speculative. Alekhine is not hoping the attack arrives — he can see the mate on move 30 before he plays move 26.