Exchange Variation

The Exchange Variation, 3...exd4, is Black's most frequent answer to 3. d4 in the Philidor Defense. It releases the tension at once. Black does not try to hold a strongpoint on e5, as with 3...Nd7 or 3...Nf6, and instead gives up the center to gain freedom for the pieces. The resulting structure sets White's pawn on e4 against Black's pawn on d6. White has more space, while Black has a compact position that is hard to break open. The pawn on d6 still shuts in the dark-squared bishop, so the question of where to develop it shapes the variation.

White nearly always recaptures with the knight, 4. Nxd4, which accounts for about seven games in ten. Taking with the queen, 4. Qxd4, is playable, but the centralized queen can be hit by ...Nc6, and Black gains a tempo. With the matter of e5 settled, Black's priority is to finish development before falling too far behind. The usual scheme is 4. Nxd4 Nf6 5. Nc3 Be7, followed by ...O-O. White ends up with the half-open d-file and Black with the half-open e-file. Black's counterplay depends on active pieces and pressure against the pawn on e4. The result is a cramped but resilient defensive position rather than a sharp fight.

Two other treatments of the f8-bishop have been tried. In the Larsen Variation, 4...g6, Black fianchettoes it on the long diagonal. The Paulsen approach plays an early ...d5, and after exd5 Black recaptures with the queen. Both are generally considered too slow to equalize comfortably.

White can also leave the pawn on d4 and play for development. With 4. Bc4, the Morphy Gambit, White brings the bishop out toward f7 before regaining material. With 4. c3, the Bird Gambit, White offers a pawn to open lines. Both are minor options compared with 4. Nxd4, and the Bird Gambit produces the best results for White among the main fourth moves.

Engines rate the position as a slight edge for White, and White scores somewhat better in practice. Draws are uncommon in the database, at only about four percent of games. The variation is among the more frequently reached named positions in online play.