Exchange Variation, Bulla Attack

The Bulla Attack replaces the usual 4. Bd3 or 4. c4 with the flank advance 4. g4, an attempt to unbalance the otherwise symmetrical Exchange Variation structure. The g-pawn takes the f5-square from Black's light-squared bishop and claims kingside space. It does so at the cost of a tempo that develops no piece and of loosening the squares around White's own king. It is a rarely played sideline, met far less often than the main continuations.