Anglo-Slav Variation, Bogoljubow Variation

After 1. Nf3 d5 2. c4 c6, Black supports the d5-pawn in Slav fashion, and play often drifts into Queen's Gambit Declined or Slav structures once White advances d4. With 3. b3, White avoids that transposition. The c4-pawn stays as the only central pawn, the dark-squared bishop heads for b2, and a later g3 and Bg2 can add a second fianchetto. This is the double-fianchetto scheme of the Anglo-Slav Variation, here reached through the Réti move order rather than via 1. c4. Black keeps a classical pawn center and can choose how to develop.

3...Nf6 is by far the most common reply. 3...e6, 3...Bf5 and 3...Bg4 are less frequent. The bishop moves develop the light-squared bishop outside the pawn chain before ...e6 shuts it in, and the engine favors them alongside 3...Nf6. After 3...e6, White has scored somewhat better in practice. The Stonewall Line arrives at the same kind of setup by another route: 1. Nf3 d5 2. c4 e6 3. g3 Nf6 4. Bg2 Be7 5. O-O O-O 6. b3 c6 7. Bb2. The engine rates the position after 3. b3 as balanced, and overall results lean slightly toward White.