When you can reach the same kind of position with or without a check, add up the plusses and minuses.
Oleg Romanishin White
Vasily Ivanchuk Black
Irkutsk 1986
French Defense, Advance Variation C02
1 e4 e6 2 d4 d5 3 e5 c5 4 c3 ♘c6 5 ♘f3 ♗d7 6 ♗e2 f6 7 0-0 fxe5 8 ♘xe5!
With Black’s kingside weakened somewhat, White eyes ♗h5+.
8...♘xe5 9 dxe5 ♕c7
Black threatens ...♕xe5 and prepares ...0-0-0, e.g. 10 ♗f4 ♘e7 and ...♘g6.
10 c4! ♕xe5
Now 11 ♗f3 would threaten 12 cxd5 (12...exd5?? 13 ♖e1).
11 ♗h5+!? g6 12 ♗f3
Black sees ...g6 as a free move. White sees how f6 is weakened.
12...0-0-0 13 ♖e1 ♕d6 14 ♘c3
That weakening counts after 14...♘f6 15 ♗g5!. For example, 15...♗e7 16 cxd5 exd5 17 ♖xe7 ♕xe7 18 ♘xd5. Or 17 ♘xd5 ♘xd5 18 ♗xe7.
14...dxc4
Black’s problems are further shown by 14...d4 15 ♕b3 ♕b6 16 ♘b5. Then 16...a6? 17 ♘d6+! (17...♕xd6 18 ♕xb7 mate).
15 ♕e2 ♘f6 16 ♕xc4 ♗e7 17 ♗f4 ♕d4?
Black is in bad shape following 17...♕b6 18 b4.
Question 373: And on 18...♕xb4 ?
18 ♘b5! ♗xb5 19 ♗xb7+! resigns.
Mate in two moves.
Antti Pyhala White
Rikard Backelin Black
Stockholm 1987
1 e4 e6 2 d4 d5 3 e5 c5 4 c3 ♘c6 5 ♘f3 ♗d7 6 ♗e2 f6 7 0-0 fxe5 8 ♘xe5 ♘xe5 9 fxe5 ♕c7 10 c4 ♕xe5 11 ♗h5+ g6 12 ♗f3 0-0-0 13 ♖e1 ♕c7 14 cxd5 ♗d6? 15 ♗g5! ♘e7 16 ♘c3 ♖de8? 17 dxe6 ♗c6 18 ♗xc6 ♕xc6 19 ♘e4 ♘f5 20 ♘xd6+ ♘xd6 21 ♖c1 ♖hf8 22 b4! c4 22 b5 ♕c7 23 ♕d4! ♘xb5 24 ♕xc4 ♕xc4 25 ♖xc4+ ♔b8 26 e7 resigns.