Zukertort Defense

The Zukertort Defense is a collective name for unusual answers to 1. Nf3 that begin with an early knight move to the edge of the board. Two lines carry names: the Sicilian Knight Variation, 1. Nf3 Na6 2. e4 c5, and the Kingside Variation, 1. Nf3 Nh6 2. d4 g6. The label comes from the opening move itself, which some sources call the Zukertort Opening after Johannes Zukertort, who used 1. Nf3 in his 1880 match with Samuel Rosenthal and occasionally afterward; others call 1. Nf3 the Réti.

The usual way for Black to meet 1. Nf3 is to deny White 2. e4 with 1...Nf6 or 1...d5. Both rim-knight moves do the opposite: they exert no influence on e4 or d4, so White can take a broad share of the center at once, as both named lines show. In return Black keeps every pawn flexible and leaves White to guess which structure is coming, at the cost of a knight that controls fewer squares than it would on c6 or f6 and usually needs another tempo to find a better post.

In the Sicilian Knight Variation, Black follows 2. e4 with ...c5, and the resulting position is the same one that arises from 1. e4 c5 2. Nf3 Na6. Play therefore takes on a Sicilian character, with the a6-knight eyeing c7, b4 and c5 rather than pressing on d4 from c6. The Kingside Variation instead pairs the h6-knight with a kingside fianchetto after 2. d4 g6. Here the knight can head for f5 to bear on d4, and keeping it off f6 leaves both the f-pawn and the long diagonal unobstructed, giving the setup some kinship with Modern Defense structures.

Both branches are rare and sit well down the list of named openings by number of games. Little established theory exists for either, so the play tends to be decided by general understanding of the structures rather than memorized lines, and White, with central pawns already placed, has an easy choice of setups.