Rat Defense

The Rat Defense is an umbrella name for Black setups that begin with an early ...d6, most often 1. e4 d6, classified under ECO B00. The pawn move does not occupy the center. It covers e5, so that ...Nf6 can follow without being driven back by e4-e5. Because Black commits so little, many games pass into the Pirc Defense, for instance 2. d4 Nf6 3. Nc3 g6, where 4. f4 is the Austrian Attack. White's 2. Nf3 blocks the f-pawn and gives up the f4 setup. It also lets Black choose 2...c5 for an Open Sicilian or 2...e5 for a Philidor. The starting position is reached often and ranks among the hundred most frequent named positions.

Several replies give Black a game of its own. After 1. e4 d6 2. d4, the Antal Defense 2...Nd7 develops the queen's knight first. It backs a later ...e5 and delays the decision about ...Nf6. The Balogh Defense 2...f5 attacks e4 with the f-pawn in Dutch style, accepting looser kingside light squares in exchange for immediate central friction. The Accelerated Gurgenidze arises from the Modern order 1. e4 g6 2. d4 d6 3. Nc3 c6, adding an early ...c6 to the fianchetto setup. The Small Center Defense, 1. d4 e6 2. e4 d6, puts Black's pawns on e6 and d6 and concedes space while keeping the position compact.

White can also leave the main paths at move two. The Harmonist, 1. e4 d6 2. f4, takes kingside space before d4 is played. Black can then reply 2...d5 3. exd5 Nf6, the Fuller Gambit, which moves the d-pawn a second time and offers it for development against a position already loosened by f4. The Petruccioli Attack 2. h4 and the Spike Attack 2. g4 are flank thrusts seen mainly as surprise weapons. Against the queen's pawn, the English Rat, 1. d4 d6 2. c4 e5, uses the early ...d6 to support an immediate strike at d4. Black does this before committing the king's knight.

The approach goes back to 19th-century India. Moheschunder Bannerjee used 1...d6 against 1. e4 to prepare ...Nf6, and his games became known in the West through John Cochrane. The main transpositional destination, the Pirc, takes its name from Vasja Pirc (1907–1980). The Pirc is closely tied to the Modern Defense, 1...g6, and the two are sometimes grouped together as the Pirc-Robatsch.