Under-promotion is not used very often in a game of chess as an amateur or beginner automatically reaches for a queen when his pawn reaches the eighth rank. However, under certain positions, it is beneficial to opt for a rook, bishop or knight, it checks the opponent's King.
In the game which follows, Black accepts the King's Gambit and plays daringly by advancing all his Kingside pawns.
White is a trifle passive and has to watch helplessly as his opponent under-promotes a pawn into a knight, not once but twice in a matter of moves. White's King is in a check and the moves are more or less forced for him.
White: George Alcog MacDonnell; Black: Henry Bird
England, 1875
The King's Gambit
1. e4 e5 2. f4. The King's Gambit enjoyed a great popularity then. White sacrifices an early pawn for attack.
2. ... exf4. This was the romantic era of chess and a Gambit had to be accepted
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3. Nf3 g5. Once he has accepted the pawn he has all intentions of defending it.
4. h4 g4 5. Ne5 h5 6. Bc4 Nh6 7. d4 d6. He can play 7. ... Qf6 or 7. ... Be7 8. Bxf4 Bxh4+ 9. g3 but this does look better for white.
9. g3. There was no need for White to play this when he had several options at his disposal. He could have played 9. gxf3 gxf3.
9. ... f5.
Black has pushed all his Kingside pawns and the position looks very unfamiliar with most pawn moves and the pieces still on their original squares. If 9. ... Be6 10. Bb3 Bxb3 11. axb3 f6 12. Nc3 c6 13. Nf4 Nf7 14. Ne6 Qe7 15. d5 Ne5 16. Bf4 Bh6 17. Kf2 with a good position for White.
10. Nc3 fxe4 11. Nxe4 Nf5. Still moving the same knight. If 11. ... d5 12. Bxd5 Qxd5 13. Nf6+
12. Kf2. The King tries to find a safe square for himself.
12. ... Be7 13. Nf4 Rh7 14. Ng6. Going into enemy territory but he would have been better off with 14. Re1 and attain equality.
14. ... d5 15. Nxe7. This was needless. White has wasted moves in taking the knight into enemy territory and then exchanged it without the slightest improvement in position.
15. ... dxe4 16. Nd5. Not a good move once again. Better was 16. Nxf5! Bxf5 17. Bg5 where White would not have been worse.
16. ... Be6 17. Bg5 Bxd5. Black livens up the proceedings by sacrificing his queen.
18. Bxd8 e3+ Black's pawn is in the centre and the Kingside has advanced too much for White's comfort.
19. Kg1 Bxc4 20.Bg5 f2+ The pawns are a pain for White now as they are advancing menacingly with support.
21. Kh2 e2 22. Qd2.
Diagram 1
22. ... f1 (N+) and Black under-promotes his pawn into a knight with a check rather than a queen.
23. Rhxf1. He has no choice here.
23. ... exf1N+ Another pawn promotes into a second knight, with a check once again.
24. Rxf1 Bxf1 25. Qe1+ Ne7 26. Qxf1 Nbc6 27. d5 Rf7 28. Qc4 If 28. Qb5 0-0-0 29. dxc6 Rd2+ 30. Kg1 Nxc6 with advantage for black.
28. ... Ne5 29. Qxc7 Nf3+ 30. Kg2 Rc8. Moving with a threat.
31. Qa5 Rxc2+ The White King has been vulnerable throughout the game as first the pawns were targeting him and now the other pieces.
32. Kf1 Nxg5+ Capturing with a discovered check.
33. Ke1 Nf3+ 34. Kd1 Rd2+ 35. Kc1 Nxd5 36. a3 Rc7+ 37. Kb1 Nc3+ The final finishing touches are given with a knight sacrifice.
38. bxc3 Re7 and white resigned as he cannot avert checkmate.
Diagram 2
White to play and win
1. Qc5. And it is all over for Black.
Diagram 1
