Ruy Lopez, Morphy Defense

Coordinates in algebraic notation use a column letter and row number; a6 is column a, row six. The Morphy Defense is defined by Black’s a6 advance. The pawn attacks White’s bishop on b5 and demands a decision. It does not win the bishop by force: White can capture the knight on c6 or retreat the bishop to a4. The value of a6 is to gain information and prepare new options, not to trap the piece immediately.

The bishop’s two main decisions

• If the bishop captures on c6, Black commonly recaptures with a pawn. Black may receive doubled pawns, two black pawns on the c-file, but keeps the bishop pair, meaning both bishops remain available to work together.
• If the bishop retreats to a4, it keeps pressure on the knight, while Black can gain space with b5 or bring out the g8-knight.

The Morphy Defense is more a gateway than a complete plan. After a6, many families become possible, including the Modern Steinitz and the Neo-Arkhangelsk. To understand the position, watch Black’s next decision: support the center, bring out a piece, gain space, or open the game.