The idea in one sentence
Black takes the c4 pawn, not to keep it but to free development and hit d4 with ...c5.
♔ White's plans
- Win the pawn back with e3 and Bxc4
- Use the centre: e4 or d5
- Keep the isolated d-pawn active if it appears
♚ Black's plans
- Take on c4 and return it
- Strike d4 with ...c5
- Gain queenside space with ...a6 and ...b5
Pawn structure. Often White gets an isolated d-pawn; Black aims to blockade it.
How to learn it
- Read the idea and the plans: every move below serves one of them.
- In the story, ask of each move: what does it do, what does it stop, what does it prepare, why not the other one?
- Drill your side. At the key moves you name the idea first, then play the move.
- Missed moves come back first next time, and in your journal.
The defining moves
- 2...dxc4 takes the pawn; trying to keep it would cost too much.
- 4.e3 opens the bishop's path to c4 to win the pawn back.
- 5...c5 hits d4 at once.
- 6...a6 prepares ...b5, gaining space with tempo on the bishop.
The line follows the moves masters play most (Lichess masters database), each checked by Stockfish 19 at depth 22; where the book move is not Stockfish's first choice, the story says so. Scores are in pawns from White's side: +0.30 is good for White, −0.30 for Black.