Morphy Defense, Modern Steinitz Defense

The Modern Steinitz Defense, 4...d6, also known as the Deferred or Neo-Steinitz Defense, is Black's most common fourth-move alternative to 4...Nf6. The pawn settles the defense of e5 for good and opens a path for the c8-bishop, but it hems in the king's bishop and turns the pressure on c6 into a real pin. The difference from the old Steinitz, 3...d6, is that ...b5 can cut the pin at any moment, so Black keeps the e5 stronghold. After 5. d4 b5 6. Bb3 Nxd4 7. Nxd4 exd4, the recapture 8. Qxd4 loses to the Noah's Ark Trap: 8...c5 9. Qd5 Be6 10. Qc6+ Bd7 11. Qd5 c4, as in Steiner–Capablanca, Budapest 1929.

White usually castles or plays 5. c3, which prepares d4 and gives the bishop a retreat on c2. Black typically unpins with ...Bd7 and often fianchettoes with ...g6 and ...Bg7. The line 5. c3 Bd7 6. d4 leads to slow maneuvering, whereas the Siesta Variation, 5. c3 f5, and 5. O-O Bg4 6. h3 h5 produce sharp play. Alekhine, Capablanca and Keres played it often, and Steinitz himself switched to this move order in his 1895 rematch with Lasker. Today it is a minor sideline, used at high level mainly as a less theoretical surprise in faster games. Engines give White a slight edge.