Morphy Defense

The idea

3...a6 asks the bishop to decide at once: retreat or exchange itself for the knight on c6. Most players retreat with 4.Ba4, keeping the pressure on c6, and Black can later chase the bishop further with ...b5.

It is Black's most popular reply to the Ruy López, and it leads to the Closed and Open variations after 4.Ba4 Nf6 5.O-O.

Plans for White

4.Ba4 keeps the pin's pressure. Then castle, play Re1 and c3, and prepare d4. The bishop usually ends up on b3 or, later, c2.

4.Bxc6, the Exchange Variation, is a different plan: White gives up the bishop to damage Black's pawns and aims for a good endgame.

Plans for Black

Develop with ...Nf6 and ...Be7, and choose the character of the game: the solid Closed Variation with ...b5 and ...d6, or the active Open Variation with ...Nxe4.

Watch out for

For White, the Noah's Ark Trap. If Black plays ...d6 and ...b5, and White wins a pawn with d4 and Qxd4, then ...c5 and ...c4 trap the bishop on b3. Even strong players have fallen for it: Endre Steiner did against José Raúl Capablanca in Budapest in 1929.

For Black, playing ...b5 too early. It weakens the queenside, and White can sometimes attack it with a4.