As a beginner, you learned that two pieces can’t occupy the same square.
You soon learn why that’s a tactical problem.
Svetozar Gligoric White
Roman Toran Black
Havana 1952
Caro-Kann Defense B17
1 e4 c6 2 ♘c3 d5 3 ♘f3 dxe4 4 ♘xe4 ♘d7 5 d4 ♘df6
More common is 5...♘gf6. But after 6 ♘g3 the d7-knight has nowhere promising to go but b6. And until that knight moves, the c8-bishop has no moves.
In contrast, there is no traffic jam after 5...♘df6 6 ♘g3 ♗g4! and ...e6.
6 ♘c5! g6?
Not 6...♗f5? or 6...♗g4? in view of 7 ♘xb7.
But after 6...g6 Black’s g8-knight becomes a problem piece because its best square, f6, is occupied. Better was 6...e6 7 ♘d3 ♗d6 and 8...♘e7.
7 ♗c4 ♘h6
Black anticipates an attack on f7.
8 ♘e5! e6 9 ♕f3 ♘f5 10 c3 ♗g7 11 ♗g5!
The pin is strong because the f5-knight can be pressured by ♘e4 or g2-g4.
For instance, 11...h6 12 ♗xf6! ♕xf6 13 ♘e4 ♕e7 14 g4!.
Then 14...♘d6? 15 ♘xd6+ ♕xd6 16 ♕xf7+ and wins. Or 14...♘h4 15 ♘d6+! ♕xd6 16 ♕xf7+.
11...0-0? 12 ♘e4!
Black cannot get out of the pin.
12...h5
13 g4! c5 14 gxf5 resigns.
Igor Solomunovic White
Thortsen Mueller Black
Bavaria 1997
1 e4 c6 2 d4 d5 3 ♘c3 dxe4 4 ♘xe4 ♘d7 5 ♘f3 ♘df6 6 ♘c5 e6 7 ♘d3 ♗d6 8 g3 ♘e7 9 ♗g2 ♕c7 10 0-0 ♘g6 11 ♖e1 ♘d7 12 b3 ♗e7 13 c4 ♗f6 14 ♗a3 ♗e7 15 ♗b2 0-0 16 h4! ♘f6 17 ♘g5 ♖d8? 18 h5 ♘f8? 19 ♘e5! ♘6d7 20 ♘gxf7 ♖e8 21 d5 ♘xe5? 22 ♗xe5 ♕b6 23 ♕g4 g6 24 ♘h6 mate.
Question 110: What about 21...♗f6 ?