King's Indian Defence

The idea

Black allows White a broad pawn centre without contesting it immediately, developing with g6, Bg7 and short castling instead. The point comes later: Black strikes at the centre with e5 or c5, and if White locks the position with d5, the game becomes a race between a Black kingside attack and a White queenside one.

Typical plans

• As Black, after d5 by White, play f5 and then f4, g5, g4 in a direct pawn storm at the king.
• As White, meet the attack with a fast c5 break and play on the queenside, where you are much closer to the target.
• As White, avoid the whole race with the Exchange Variation and head for a level endgame.

What goes wrong

• As Black, starting the attack before it can be supported by pieces. Timing is the entire opening.
• As White, defending passively on the kingside. Counterplay on the other wing is faster than defence.
• Both sides underestimating how sharp the mutual race becomes. Half a tempo decides these games.

Using the board above

The board starts at the position after 1. d4 Nf6 2. c4 g6 3. Nc3 Bg7. Play the continuation you normally meet, then ask the engine what it would do. That is more useful than reading a line, because it answers the question you actually have, which is what happens in the position you keep reaching.

One caution worth carrying into it: an engine evaluates an opening on the assumption that both sides then play perfectly. A line rated a tenth of a pawn better whose middlegames you have never played is worth less to you than a line rated slightly worse that produces positions you understand. More on that here.