Nimzo-Indian Defense

Black often gives the bishop for the knight on c3. White gets two bishops and a broad centre; Black gets a target, the doubled pawns on c3 and c4. Black's whole strategy is to keep the position closed (so the bishops stay passive) and attack c4 with ...b6, ...Ba6, ...Nc6-a5 and ...Rc8.

White develops calmly and castles, keeping the option of recapturing on c3 with a pawn only when it suits. The main line leads to classical central tension: Black chooses between taking on c4, keeping the tension with ...Nc6, or trading on c3 to fix the doubled pawns.

With the queen on c2, White can recapture on c3 with the queen and keep a healthy pawn structure plus the bishop pair. The cost is time: the queen moves twice and the kingside is undeveloped. Black uses that time for ...b6, ...Bb7 and control of e4.

The b4 bishop has no pawn protecting it. As long as a knight on c6 or d7 or the queen on d8 or e7 covers it, all is well, but the moment Black plays ...b6 or ...d6 at the wrong time, Qa4+ (checking the king and hitting b4) wins it. It is by far the most common tactical theme in this opening.

Black gives up the bishop at once and builds a dark-square blockade with ...d6 and ...e5. White's bishops bite on granite, and the c4 pawn becomes a long-term weakness. Fischer used this setup against Spassky in their 1972 world championship match.

White answers pin with pin: the bishop on g5 or h4 pins the f6 knight to the queen on d8. Black normally breaks it with ...c5 and ...d6 or ...g5, but moving the knight while the pin is on (typically ...Ne4) simply loses the queen.

After taking on c3 and c4, Black puts the queen on c7 and pushes ...e5, trading White's central pawns and aiming the pieces at the weak c3 pawn. White keeps the bishop pair and hopes to open the position with e4 or a4-a5.

With the bishop pair and doubled pawns that can't be defended forever, White plays for a big centre with f3 and e4, then f4-f5 against Black's king. Black blockades with ...e5 or ...Na5 and ...Ba6 against c4. Whoever achieves their plan first usually wins.

Black's pawns on c5, d6 and e5 fix the dark squares and take the air out of White's bishops. The plan is ...b6, ...Na5 and ...Ba6 against the c4 pawn, with ...e4 always in the air if White opens the centre carelessly.

After winning the bishop pair without structural damage, White's task is to catch up in development: e3, Bd3 and Ne2, often with f3 to take e4 from Black's pieces. If White castles safely, the two bishops give a lasting edge; if not, Black's lead in development tells.

When White avoids the doubled pawns with Ne2, Black immediately attacks the c4 pawn with the bishop, forcing White to spend time defending it. After ...d5 Black has a solid centre and good play on the light squares.