1.e4 e5 2.Nf3 Nc6 3.Bb5 a6 4.Ba4 Nf6 5.0-0 b5 6.Bb3 Bc5
The system presented here is called the Möller or Modern Arkhangelsk Variation. It is currently very popular at the top level, as it fulfils the desire of many grandmasters for active counterplay with Black, e.g. Alexei Shirov and Viswanathan Anand have often played it. In the original Arkhangelsk Variation (5...b5 6.Bb3 Bb7) Black immediately develops the queen's bishop to b7. In the old form of the Möller Variation, 5...Bc5 is played before ...b5. The modern system with 5...b5 6.Bb3 Bc5 has emerged as a mix of the two.
In the Möller system the bishop is brought in front of the pawn chain, only then is the important central point e5 supported with ...d7-d6. The white-squared bishop has the option of taking up position on b7 or working actively on the c8-h3 diagonal, where it could pin the Nf3 with ...Bg4. From White's point of view, the standard plan c2-c3 together with d2-d4 comes into question in any case, and the advance a2-a4 is also very important, which after axb5 axb5 gives Black a weak pawn on b5. This pawn is often attacked with Nb1-a3 and captured or sacrificed by Black. In many variations, the Bc1 can set up an unpleasant pin against the Nf6 with Bg5, which cannot be parried with ...Be7 due to the active position of the Bc5. However, unleashing with ...h7-h6 and ...g7-g5 is an option, although it must be carefully considered whether this does not weaken Black's position on the kingside too much.
A typical sequence of moves could look like this: 7.a4 Rb8 8.c3 d6 9.d4 Bb6 10.axb5 axb5 11.Na3 0-0 12.Nxb5 Bg4.
White has captured the b5-pawn, but the price is the pressure of the black minor pieces on the e4- and d4-pawns. In addition, the Nf3 is pinned and the Nb5 is indirectly attacked by the Rb8. White has already tried a lot in this position, especially 13.Bc2, 13.d5 and 13.Re1. An alternative for White in the first diagram is the move 7.Nxe5, because after 7...Nxe5 the fork 8.d4 wins back the piece. After 8...Bxd4 9.Qxd4 d6, however, there is nothing wrong with Black's position. If you enjoy following the current grandmaster games, you will certainly often be offered something new about this system. The theory is developing rapidly and it's worth keeping up to date.