Main lineA47
1. d4 Nf6 2. Nf3 b6 3. g3 Bb7 4. Bg2 c5
White's kingside bishop takes the long diagonal and Black's queenside bishop takes the long diagonal.
A47
Marienbad System
2 named lines in this family, ECO A47. Every one of them opens 1. d4 Nf6 2. Nf3 b6, so the notes on those moves are written once, just below, instead of once per line. Under each line you get its moves and the sentences it adds that this page has not already printed. A line's own page carries up to its first 4 per-move notes in full.
The moves every line here plays
1. d4 Nf6 2. Nf3 b6
- 1. d4 Stakes a claim in the centre, controlling e5, and frees the bishop and queen.
- 1... Nf6 Develops the knight to f6, eyeing d5 and e4.
- 2. Nf3 Develops the knight to f3, eyeing d4 and e5. It also props up the d4 pawn. Theory calls this the Knights Variation.
- 2... b6 Prepares the fianchetto: the bishop will take the long diagonal via b7. Theory calls this the Pseudo Queen's Indian Defense.
Berg VariationA47
1. d4 Nf6 2. Nf3 b6 3. g3 Bb7 4. Bg2 c5 5. c4 cxd4 6. Qxd4
An early pawn trade leaves the c-file as Black's avenue and the d-file as White's - both sides get real winning chances down their own file.
Walk these lines on a board
An account opens every move's note in this family, the plan behind each line, and a trainer that plays the line back at you. It is free.