The Semi-Tarrasch Defense, San Sebastian Variation is a variation of the Queen's Gambit Declined, catalogued as ECO D41. The line runs 1. d4 d5 2. c4 e6 3. Nc3 Nf6 4. cxd5 Nxd5 5. e4 Nxc3 6. bxc3 c5 7. Nf3 cxd4 8. cxd4 Bb4+ 9. Bd2 Qa5, reaching the position shown below after 18 half-moves.
White holds the centre with pawns on d4 and e4. Development is level at three minor pieces each. It is White to move after nine moves. White’s a-file pawn is isolated; the c-file file is fully open.
On the Queen's Gambit Declined generally: A solid and respected response to the Queen's Gambit. Black maintains a strong central presence.
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The Semi-Tarrasch Defense, San Sebastian Variation goes 1. d4 d5 2. c4 e6 3. Nc3 Nf6 4. cxd5 Nxd5 5. e4 Nxc3 6. bxc3 c5 7. Nf3 cxd4 8. cxd4 Bb4+ 9. Bd2 Qa5. It is a variation of the Queen's Gambit Declined and is catalogued as ECO D41.
The Semi-Tarrasch Defense, San Sebastian Variation is ECO D41. ECO codes group openings by their move order, so nearby codes cover closely related lines of the Queen's Gambit Declined.
Stockfish evaluates the position after 1. d4 d5 2. c4 e6 3. Nc3 Nf6 4. cxd5 Nxd5 5. e4 Nxc3 6. bxc3 c5 7. Nf3 cxd4 8. cxd4 Bb4+ 9. Bd2 Qa5 at +0.95 at depth 18, which is a small but real edge for White. Engine evaluation is only a starting point — at club level the practical value of a line is mostly about whether you know its plans better than your opponent does.
White holds the centre with pawns on d4 and e4. Development is level at three minor pieces each. It is White to move. White’s a-file pawn is isolated; the c-file file is fully open.