Three Knights Variation

The Three Knights Variation is the standard main-line position of the Slav Defense, reached by 1. d4 d5 2. c4 c6 3. Nf3 Nf6 4. Nc3. The knight on c3 puts a second piece on d5 and controls e4, the square White normally aims to occupy with a pawn. It could also go to d2, but from c3 it leaves the diagonal of the c1-bishop open. Black must now commit to a plan for the queen's bishop and for the tension between d5 and c4. Every reply stays within the Slav family, yet the resulting games differ widely in structure and character.

The most frequent answer is 4...e6, which enters the Semi-Slav Defense. Black accepts a temporarily passive light-squared bishop behind the c6–d5–e6 chain and plans to release it later with ...c5 or ...e5. The Semi-Slav is a large and complex opening in its own right.

The next most common replies develop the bishop at once. 4...Bf5 and 4...Bg4 together account for over two-fifths of the games in the database. Both put the bishop outside the pawn chain while Black keeps the d5-pawn in the center. 4...dxc4, the Pure Slav, takes the opposite approach. Black gives up the center for a while and develops the bishop to f5 or g4 while White spends time recovering the pawn. Its usual continuation, 5. a4 Bf5, is the Czech Variation.

The quieter options keep the bishop's choices open. 4...a6, the Chebanenko Variation, prepares ...b5 without shutting in the bishop. In the database it gives Black slightly better results than the other main replies. 4...g6, the Schlechter Variation, fianchettoes the king's bishop instead. It is far less popular, partly because in exchange structures the move ...a6 tends to be more useful to Black than ...g6. 4...Qb6, the Süchting Variation, is a rare sideline.

The engine rates the position as roughly balanced. Its preferred moves are 4...e6, 4...a6 and 4...dxc4 rather than the immediate bishop sorties. In online games White scores a little over half, and draws are uncommon.