411 REFERENCE · Wikibooks
Chess Opening Theory/1. e4/1...e5/2. Nf3/2...Nc6/3. Bb5/3...Nd4/4. Bc4
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Ruy Lopez: Bird Variation rd bd qd kd bd nd rd pd pd pd pd pd pd pd pd bl nd pl nl pl pl pl pl pl pl pl rl nl bl ql kl rl
4. Bc4
White retreated the attacked bishop, who is now targeting f7. Common moves in this position are 4...Nxf3+ and /4...Bc5/.
Ruy Lopez, Bird's Defence