Queen's Knight Variation

3. Nc3 is White's most common third move in the Queen's Gambit Declined. The knight puts a second piece on d5 and covers e4, the square White would like to claim with an eventual e2-e4 advance. The position also arises from the English Opening via 1. c4 e6 2. Nc3 d5 3. d4. Black now chooses between several established systems, and the engine rates the position as close to level. In practice White scores a little better.

3...Nf6, the Normal Defense, accounts for more than half of all games. It guards d5 and stops e4. However, it also removes the queen's cover of g5, so White can pin the knight with 4. Bg5. The alternatives 4. cxd5 and 4. Nf3 lead to the Exchange Variation and the Three Knights.

Two replies prepare to take on c4 and support the pawn with ...b5. After 3...c6, 4. Nf3 dxc4 leads to the sharp Noteboom Variation, while 4...Nf6 is a Semi-Slav. White can also exploit the fact that ...c6 neither develops a piece nor watches e4 by playing 4. e4, the Marshall Gambit. There White gives up a pawn in return for the two bishops and chances against the black king. A third option, 4. e3, can lead to a Stonewall Dutch after ...f5. The Janowski Variation, 3...a6, has the same capturing idea and has gained followers in recent years. It usually prompts White to release the tension with 4. cxd5. The immediate 3...dxc4 is fairly common, but White scores noticeably well against it.

3...Be7, called the Alatortsev or Charousek Variation, holds back the king's knight so that Bg5 no longer pins anything. It also sidesteps the main Exchange line, 3...Nf6 4. cxd5 exd5 5. Bg5. White can head back to familiar territory with 4. Nf3 Nf6 5. Bg5. At top level, however, 4. cxd5 exd5 5. Bf4 c6 6. e3 is more popular. In that line 6...Bf5 7. g4 became topical after Botvinnik used it in his 1963 title match with Petrosian. 3...c5 is the Tarrasch Defense, in which Black usually accepts an isolated d-pawn in exchange for free piece play.

The engine's first choice is 3...Bb4, the Accelerated Ragozin, which aims for Ragozin or Nimzo-Indian positions. Its drawback is 4. a3 Bxc3+ 5. bxc3 Nf6 6. e3. This produces the structure of Botvinnik–Capablanca, AVRO 1938, generally judged slightly favorable to White, who can later undouble the c-pawns with cxd5. 3...b6, the Alapin Variation, is rarely played.