The Open, Harksen Gambit is a variation of the Ruy Lopez, catalogued as ECO C80. The line runs 1. e4 e5 2. Nf3 Nc6 3. Bb5 a6 4. Ba4 Nf6 5. O-O Nxe4 6. d4 b5 7. Bb3 d5 8. c4, reaching the position shown below after 15 half-moves.
Both sides have pawns in the centre (White on d4, Black on d5 and e5), and three pawn captures are available, so the structure is still fluid. Development is level at two minor pieces each, and Black is up a pawn of material. It is Black to move after eight moves. White has castled while Black’s king is still uncommitted.
On the Ruy Lopez generally: One of the oldest and most classical openings. White develops rapidly and puts pressure on Black's center.
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The Open, Harksen Gambit goes 1. e4 e5 2. Nf3 Nc6 3. Bb5 a6 4. Ba4 Nf6 5. O-O Nxe4 6. d4 b5 7. Bb3 d5 8. c4. It is a variation of the Ruy Lopez and is catalogued as ECO C80.
The Open, Harksen Gambit is ECO C80. ECO codes group openings by their move order, so nearby codes cover closely related lines of the Ruy Lopez.
Stockfish evaluates the position after 1. e4 e5 2. Nf3 Nc6 3. Bb5 a6 4. Ba4 Nf6 5. O-O Nxe4 6. d4 b5 7. Bb3 d5 8. c4 at -1.19 at depth 18, which is a small but real edge for Black. 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.
Both sides have pawns in the centre (White on d4, Black on d5 and e5), and three pawn captures are available, so the structure is still fluid. Development is level at two minor pieces each, and Black is up a pawn of material. It is Black to move. White has castled while Black’s king is still uncommitted.