Anglo-Indian Defense, Hedgehog System

The Hedgehog System (ECO A17), 1. c4 Nf6 2. Nc3 e6, is the Anglo-Indian move that prepares ...Bb4. With White's knight already on c3, that pin loosens White's control of d5 and raises the prospect of doubled c-pawns. The move also keeps ...b6 and ...Bb7 in reserve for a Queen's Indian setup. Because White has not yet committed the d-pawn, Black can often develop quickly and wait to see which structure White chooses. The ECO label covers the whole position after 2...e6. The formation known as the Hedgehog in Symmetrical English lines, with ...b6, ...e6, ...Bb7 and ...Be7 followed by ...a6 and ...d6, is only one of the setups Black can reach from it, typically after a later ...c5.

The drawback of 2...e6 is that it leaves White free to play 3. e4. This move seizes the center and threatens to drive the f6-knight away with e5, and it leads to the Mikenas-Carls Variation. Black must meet it accurately, usually with 3...d5 4. e5 (the Flohr Variation), with 3...c5 (classified separately as the Sicilian Variation), or with 3...Nc6. The play there is sharp and forcing, and White scores better with 3. e4 than with any other common third move.

The most popular reply is the quieter 3. g3, which fianchettoes the king's bishop and keeps both d4 and e4 in hand. After 3. d4, the game transposes to 1. d4 Nf6 2. c4 e6 3. Nc3, and 3...Bb4 brings about a Nimzo-Indian. With 3. Nf3, Black chooses the structure. After 3...c5, the game enters Symmetrical English territory, where the struggle centers on d4 and d5, while 3...Bb4 gives the Nimzo-English. Other possible destinations include the Queen's Indian and the Neo-Catalan.

The position is reached often, ranking in the top tenth of named openings by games played. The engine regards it as roughly balanced and prefers e4, Nf3 and d4 for White. In practice White scores somewhat better than Black. The character of the game depends almost entirely on White's third move. It can range from maneuvering Indian or Catalan-type positions to the theoretical, tactical lines of the Mikenas-Carls.