Chess Opening Theory/1. e4/1...e5/2. Nf3/2...d6/3. d4/3...exd4/4. Nxd4

= Philidor Defence: Exchange Variation 4. Nxd4 =

Overview
In the Exchange Variation of the Philidor Defense, Black opts to relieve the central tension immediately with 3...exd4. This move captures White's d4 pawn with Black's e5 pawn. In response, White has the option to recapture the pawn on d4. The most logical recapture is with the knight, 4. Nxd4, positioning the knight centrally.

After White recaptures with the knight, Black has a popular move, 4...Nf6, which targets White's e4 pawn. To defend this pawn, White often develops another piece, the queen's knight, to c3 with 5. Nc3.

An interesting alternative for Black after 4. Nxd4 is the move 4...c5. This puts immediate pressure on the centralized white knight. White would need to decide how to respond, either by relocating the attacked knight or creating a counter-threat elsewhere on the board.

The Exchange Variation with Nxd4 in the Philidor Defense leads to rich positional play. Black relieves central tension early on, but the resulting positions offer ample opportunities for both sides to create imbalances and fight for an advantage.

Theory table
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'''1. e4 e5 2. Nf3 d6 3. d4 exd4 4. Nxd4'''