Zukertort Defense: Kingside Variation is a chess opening with the ECO code A04, part of the Zukertort Defense family. It goes 1. Nf3 Nh6 2. d4 g6. White opens with 1. Nf3 (the Zukertort/Réti knight move) and Black answers 1... Nh6. After 4 moves it is White to move. The lesson on the board explains every move of the line and lets you play it yourself; it is free.