The Hippopotamus Defence is a chess opening system employed by Black, consisting of a double fianchetto structure (bishops on b7 and g7) and a small pawn centre (pawns on d6 and e6). The knights are typically developed to e7 and d7 and the rook's pawns to a6 and h6.[1] This structure can be obtained by a wide variety of move orders but it occurs most frequently via the Modern Defence (1.e4 g6) or Owen's Defence (1.e4 b6). The Hippopotamus can also be played against queen's pawn openings or flank openings and is thus a genuinely universal system. The same structure is also occasionally utilized by White.
The first master strength player to experiment with Hippopotamus-type structures would appear to have been the SlovakInternational MasterMaximilian Ujtelky.[2] The opening first came to public prominence, however, after being adopted twice by Boris Spassky in his 1966 World Championship match against Tigran Petrosian[3][4] (after which the set-up was dubbed the "Hippopotamus" by commentators). Spassky would appear to have been influenced by his 1964 game vs Ujtelky,[5] where he faced the same setup that he would later employ against Petrosian.[6]
A typical position in the Hippopotamus, White to move.
While Black sets up the Hippopotamus structure White is able to develop freely. If White proceeds in accordance with classical principles a position will arise similar to that shown in the diagram (left). Black has adopted the complete Hippopotamus set-up with pawns on a6, b6, d6, e6, g6 and h6, fianchettoed bishops on b7 and g7, and knights on d7 and e7. White, meanwhile, has occupied the centre with pawns, developed the minor pieces to central positions, castled and centralised rooks. Despite having achieved an ideal classical development White now faces a dilemma in terms of how to proceed, as Black has pawn control of every square on the fifth rank (a5-h5). White can thus only make headway by advancing a pawn into Black’s side of the board.[9]
If White should advance e4-e5, Black will typically lock the central pawns with …d6-d5. This gives rise to a central pawn structure similar to that seen in many lines of the French Defence. Black will then proceed with the typical French pawn break …c7-c5 and thematic queenside play.
Returning to the diagram position, if White should instead advance d4-d5, Black will again respond by locking the central pawns, this time with …e6-e5. The structure then resembles that seen in many lines of the King's Indian Defence. Black will likely proceed with either (a) the thematic King’s Indian pawn break …f7-f5 (usually following ...0-0), or (b) the typical Hippo idea of ...g6-g5 and ...Ne7-g6-f4, either of which plans may result in a kingside attack. Note that in positions where White intends to play d4-d5 the White queen would usually be deployed to d2 rather than e2 (thus avoiding the possibility of Black doubling White's pawns by responding to d4-d5 with ...Bg7xNc3).
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Hippopotamus Defence: French-type pawn structure (with ...c5 to follow).
If White opts against playing either e4-e5 or d4-d5, Black may begin to advance against the castled White king with moves such as …g6-g5, …Ng6, etc. (or, if White had castled queenside, …b6-b5, …Nb6, etc.). Alternatively Black might play the pawn break …c7-c5, after which the structure may transform to resemble a Sicilian (following a later …c5xd4 or d4xc5) or a Benoni (following a later d4-d5).
To allow the various options given above, Black’s main objective in the early stages will be to remain flexible, including by delaying any decision about castling until after the central pawn structure has been defined.
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Hippopotamus Defence: King's Indian-type pawn structure (with ...f5 to follow).
The Hippopotamus can be considered an anti-theory opening, with Black’s play tending to rely on a thematic understanding of the major chess openings mentioned above rather than on specific opening variations or move orders.[10]
The positions arising from the Hippopotamus differ from standard positions in the French Defence, King's Indian Defence, etc., as various pawns and pieces will be displaced compared to their usual positions in those openings. For example, in the King's Indian, Black would not have fianchettoed the queen's bishop, and White would prefer to have the c-pawn on c4 rather than c2. Hippopotamus middlegames are often defined by how the players navigate these differences and attempt to turn them to their own advantage or their opponent's disadvantage.
Hippopotamus Defence: Benoni-type pawn structure (with ...e6xd5 or ...e5 to follow).
While White can be expected to obtain a space advantage in most variations of the Hippopotamus Defence, Black will often have a practical advantage due to greater familiarity with the various transpositional possibilities in this rare opening complex. White must also be wary of playing in too aggressive a fashion or of overextending, after which the dynamism of Black's seemingly passive structure may quickly become apparent (see, for example, Barczay vs Ivkov, below).
