Chess Openings Lab
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Ruy Lopez: Bird's Defense Deferred

The Bird's Defense Deferred is 3...a6 4.Ba4 Nd4, where Black plays the knight jump only after kicking the bishop to a4. White can take on d4 and get a lead in development, while Black hopes the d4 pawn cramps White's queenside.

Moves
1.e4 e5 2.Nf3 Nc6 3.Bb5 a6 4.Ba4 Nd4
ECO
C70
Engine
+1.02 · a clear edge for White (Stockfish 17.1, depth 20)
Played
39 games in our lichess sample
White scores
52.6%

Key ideas for both sides

White

  • Take with Nxd4 and after ...exd4 castle, then use d3, Nd2 and c3 against the d4 pawn.
  • Castling first allows ...Nxf3 with check; then the queen recaptures and supports e4 and f7 pressure.
  • Keep the a4 bishop on its diagonal toward e8; it pins any piece on d7 or c6.

Black

  • After the trade, play ...c6 and ...Bc5 to support d4 and develop.
  • The knight on e7 can come to g6 or c6, adding protection to the center.
  • Use ...b5 to push the bishop to b3 and gain space on the queenside.

Plans and pawn structure

Compared with the immediate Nd4 jump, Black has played ...a6 and White's bishop is on a4. That means ...c6 does not hit the bishop, so Black has less time. White uses the lead in development to play d3, Nd2 and c3, opening the center against the d4 pawn. Black plans ...c6, ...Bc5 and ...Ne7, then castling, but White's pieces are better placed and the d4 pawn can become weak.

What the engine plays from here

Stockfish 17.1 at depth 20 rates the position +1.02: a clear edge for White. Its three top choices for White:

  1. +1.02 5.Nxd4 exd4 6.O-O c6 7.d3 Bc5
  2. +0.74 5.O-O Nxf3+ 6.Qxf3 Qf6 7.Qc3 b5
  3. +0.37 5.c3 Nxf3+ 6.Qxf3 Qf6 7.d4 exd4

Pawns, from White's side.

How to play against it

As White, take on d4, castle, and then play c3 and Nd2 to target the d4 pawn. As Black, do not expect the same play as the normal Bird: the extra ...a6 and Ba4 moves help White, because ...c6 no longer gains time against the bishop.

Questions

What are the moves of the Ruy Lopez: Bird's Defense Deferred?

The Ruy Lopez: Bird's Defense Deferred starts 1.e4 e5 2.Nf3 Nc6 3.Bb5 a6 4.Ba4 Nd4. Its ECO code is C70.

Is the Ruy Lopez: Bird's Defense Deferred good for Black?

Stockfish 17.1 rates the position +1.02 at depth 20, which is a clear edge for White. A dubious choice for Black: White gets a clear edge in development and a target, so it suits only surprise use.

What is the main idea of the Ruy Lopez: Bird's Defense Deferred?

Black plays the Bird knight jump after ...a6 and Ba4. White gets a lead in development and a target on d4 after the knight trade.

What should White play next?

The engine's first choice is Nxd4, with O-O and c3 close behind. 5.Nxd4 trades knights and leaves Black a d4 pawn that White can attack with c3 and Nd2.

Updated October 2026. Sources and method.