Sämisch 4.a3: ...c5, ...Nc6 and ...b6/...Ba6 is variation 4 of 6 in the Nimzo-Indian Defence course, a advanced opening course for Black (ECO E29). It runs 22 moves and begins 1. d4 Nf6 2. c4 e6 3. Nc3 Bb4 4. a3 Bxc3+ …. White takes the bishop pair at once but accepts doubled c-pawns. Black blocks the centre with ...c5, piles up on the weak c4-pawn with ...b6, ...Ba6 and ...Na5, and prepares ...f5 if White pushes e4 and f4. In the lesson every move is explained on a board and then drilled; it is free.
Move by move
1. d4 – White takes the centre.
1... Nf6 – Black develops.
2. c4 – White gains space.
2... e6 – Prepares ...Bb4.
3. Nc3 – White prepares e4.
3... Bb4 – Pins the knight.
4. a3 – The Sämisch: White forces the trade immediately, accepting doubled pawns for the bishop pair and a strong centre.
4... Bxc3+ – Forced, but this is exactly the structure Black wants: White's c-pawns are doubled and c4 will be a target.
5. bxc3 – White recaptures toward the centre.
5... c5 – Black hits d4 and fixes the doubled pawns; if White ever takes on c5 the pawn on c4 becomes isolated.
6. e3 – White supports d4 and prepares Bd3 and Ne2.
6... Nc6 – Develops and adds more pressure on d4.
7. Bd3 – The bishop aims at Black's king and supports e4.
7... O-O – Black castles first; White's knight is still on g1.
8. Ne2 – The knight goes to e2 so that the f-pawn stays free for f3/f4 and e4.
8... b6 – Prepares ...Ba6, the key plan against the weak c4-pawn.
The lesson goes on for 6 more moves, each with its explanation.
chessGM