Chebanenko Variation

The Chebanenko Variation, also called the Chameleon Slav and named after the theoretician Vyacheslav Chebanenko, delays the choice between ...dxc4 and ...e6. The modest 4...a6 prepares ...b5, which can either hit the c4-pawn or defend a pawn won by ...dxc4. It also makes ...Bf5 or ...Bg4 easier, because an early Qb3 can be answered by ...Ra7.

The drawback is the weakened b6-square. 5. c5 exploits it by locking the queenside and gaining space, the Advance System. Black then usually aims for ...e5 or ...b6 and often fianchettoes the king's bishop to pressure the center. White frequently puts a bishop on f4 to control e5, d6, c7 and b8, as in 5...Bf5 6. Bf4 Nbd7 7. e3 Nh5. In the database 5. Bg5 is the most common reply, followed by 5. cxd5, which releases the tension and leaves the purpose of ...a6 unclear. 5. e3 holds d4 and allows 5...b5. Engines consider the position close to balanced, and results are fairly even.