The idea in one sentence
White prepares d4 with c3, so that after a trade on d4 a pawn, not a knight, recaptures: White keeps a classical pawn centre.
♔ White's plans
- Prepare d4 with c3 and recapture with a pawn
- Kick the knight with e5 and gain space
- Develop calmly: Nf3, Bc4 or Bd3, castle
♚ Black's plans
- Attack e4 at once with ...Nf6 or ...d5
- Undermine White's centre with ...d6 and ...e6
- Use the knight on d5 actively
Pawn structure. White's isolated or full centre against Black's quick piece play.
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.c3 prepares d4 so that a pawn can recapture: White keeps two pawns in the centre.
- 2...Nf6 attacks e4 at once, before d4 comes.
- 3.e5 kicks the knight and gains space.
- 4.d4 builds the centre, as c3 prepared.
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.