A zwischenzug is simply an in-between-move that tries to dash enemy plans.
Anthony Miles White
Jan Timman Black
Amsterdam 1985
English Opening A15
1 ♘f3 ♘f6 2 c4 c5 3 b3 d5 4 cxd5 ♘xd5 5 ♗b2
White tries to impede Black’s development (5...e6 6 e3 ♗e7? 7 ♗xg7).
5...f6 6 ♘c3 e5 7 ♘xd5 ♕xd5 8 e3
The drawback to White’s plan is weakening d3. See below.
8...♗e6 9 ♗c4 ♕d7 10 0-0 ♗xc4 11 bxc4
Now 11...♕d3 12 ♕b3! ♕xb3 13 axb3 and 14 d4 favors White somewhat.
11...♗e7 12 d4! cxd4 13 exd4 exd4 14 ♘xd4
Black has problems securing his king after 14...♘c6 15 ♘xc6 ♕xc6 16 ♖e1!. For example, 16...♔f7 17 ♕h5+ g6 18 ♕h4.
14...0-0 15 ♕f3
White prepares 16 ♖ad1. He would win material after 16...♘c6 17 ♘f5 ♕c8 18 ♕g4 g6 19 ♖d7!. Also 17...♕e8 18 ♖fe1 (18...♕f7 19 ♘xe7+ ♘xe7 20 ♖d7).
15...♘c6 16 ♘f5!
White threatens 17 ♕g4 and 18 ♕xg7 mate or 18 ♘h6+ and 19 ♕xd7. He is in command after 16...♖ad8 17 ♖ad1 ♕c7 18 ♖d5! (18...♖xd5 19 cxd5 ♘e5 20 ♕e4 and ♖c1).
16...♘e5?? 17 ♗xe5 fxe5
Black’s threat of 18...♕xf5 would equalize except for:
18 ♕d5+! resigns.
After 18...♕xd5 the zwischenzug 19 ♘xe7+! wins a piece.
Question 51: Was 17 ♕d5+ just as good?
Aldo Haik White
Vadim Chuchelov Black
Hamburg 1991
1 ♘f3 c5 2 c4 ♘f6 3 b3 d5 4 cxd5 ♘xd5 5 ♗b2 ♘c6 6 e3 (6 a3!) ♘db4 7 d3 ♗f5! 8 e4 ♗g4 9 a3 ♗xf3 10 gxf3 ♘a6 11 f4 e6 12 ♘d2 ♘c7 13 ♘f3 ♘b5 14 ♗g2 ♕a5+ 15 ♕d2 ♖d8! 16 ♔e2 ♕b6 17 ♖hc1 ♗e7 18 ♖ab1 0-0 19 ♗a1? ♘xa3 and wins.