Main Line

After 1. e4 d5 2. exd5 Qxd5 3. Nc3, the retreat 3...Qa5 is the most popular way to handle the attacked queen and is generally treated as the main line. On a5 the queen is hard for White to hit again with tempo. It supports a later ...e5 and pins the c3-knight once White advances the d-pawn. In some lines it can also swing to b6 to pressure b2. Compared with 3...Qd8 it is more active, and compared with 3...Qd6 it stays away from the knight jump to b5.

White's most common replies are 4. Nf3, 4. d4 and 4. Bc4, which often transpose. Playing d4 pins White's own knight, but it clears d2 for the bishop. Once the pin is broken, the knight can move with a discovered attack on the queen. Black usually develops with ...Nf6 and either ...Bf5 or ...Bg4, and plays ...c6 to give the queen a retreat. A bishop on g4 can drop back to h5 and then g6 if White kicks it with h3 and g4. The standard sequence is 4. d4 c6 5. Nf3 Nf6 6. Bc4 Bf5 7. Bd2 e6. White then chooses between the aggressive 8. Qe2 and the quieter 8. O-O. The earlier 4. d4 Nf6, keeping ...c6 in reserve, is called the Mieses Variation.

The sharpest option is 4. b4, the Leonhardt Gambit, also known as the Mieses-Kotrč Gambit. White gives up the b-pawn to deflect the queen and gain development time. Engines regard the sacrifice as roughly balanced, some lines give White real attacking chances, and in online play it scores clearly better for White than the quiet moves. Lasker, Capablanca and Keres all tried it with reasonable results. Preparing the advance with 4. Rb1 is weaker, because 4...c5 stops the plan. A different approach is the fianchetto 4. g3, with play such as 4...Nf6 5. Bg2 c6 6. Nf3. White then aims for O-O, Rb1 and a queenside pawn push with b4 and b5, using the long diagonal against Black's queenside. Anand, Jobava, Sax and Vallejo Pons are among those who have used it.

The usual result is a stable structure in which Black's c6 and e6 pawns face White's d4 pawn. This shape is close enough to the Caro-Kann that many Caro-Kann players have taken up this line as an extra weapon. Both sides keep the option of castling on either wing. Engines give White a slight edge, while results in a large body of online games are almost exactly even.