Cozio Defense

The Cozio Defense, 3...Nge7, is an old sideline of the Ruy Lopez named after the 18th-century Italian master Carlo Cozio. Its point is that the exchange on c6 loses its sting. After Bxc6, the e7-knight takes back, so Black keeps an intact pawn structure and the e5-pawn stays protected. The cost is that the knight shuts in the f8-bishop. Black frees it in one of two ways. The knight can move again to g6, where it guards e5, or Black can fianchetto with ...g6 and ...Bg7, a setup close to the Fianchetto Defense, 3...g6.

White's most common reply is 4. O-O. There, 4...g6 keeps the knight recapture on c6 available, while 4...Ng6 makes the trade less relevant. In the Paulsen Variation, 4. Nc3 g6, White can strike with 5. d4 exd4 6. Nd5 rather than regaining the pawn at once. 4. c3, preparing d4, was a leading 19th-century choice and was favored by Carl Jaenisch. The defense was popular in that era, then gave way to 3...a6 and 3...Nf6. Bent Larsen used it occasionally, and Levon Aronian revived interest by playing it throughout the 2009 World Blitz Championship. Engines give White a slight edge, and online results are close to even.