Lesson
White to move. Main line: 1. d4 f5 2. g3 Nf6 3. Bg2 e6 4. Nf3 d5 5. O-O Bd6 6. c4 c6
Black’s pawns on f5, e6 and d5 form the Stonewall. They control e4 and support a knight on e4, giving Black a ready-made kingside plan. The cost is a fixed structure and a light-squared bishop that can struggle to find useful work.
White fianchettoes the bishop toward b7 and challenges d5 with c4. Black answers ...c6 to reinforce the center, accepting less flexibility in exchange for a stable platform from which pieces can move toward the white king.
The structure matters more than memorized move order. Black wants Ne4, Qe7 and kingside activity; White targets the light squares, trades the e4-knight and seeks pressure on the queenside. A pawn chain creates strengths and weaknesses at the same time.