Gurgenidze Counterattack

The Gurgenidze Counterattack, 3...b5, departs from the usual 3...dxe4 by preparing ...b4 to chase the c3-knight and remove a defender of e4. The flank advance costs time and loosens Black's queenside. It is considered dubious, and engines give White a slight edge. White most often answers 4. exd5, while 4. a3 discourages ...b4 and 4. e5 closes the center. It is a rare surprise weapon, yet Black scores well with it in online games.