Hippopotamus Defense

Key ideas for both sides

Plans and pawn structure

White takes the center with e4 and d4, develops with Nc3 and Nf3, and castles. The bishop on c1 often goes straight to h6 to trade off Black's knight, and after ...gxh6 Black's kingside pawns are split. Black tries to hold with ...g6 and a bishop on g7, then hits the center with ...c6 and ...d5. The engine line 2.Nc3 c6 3.d4 d5 4.Bxh6 gxh6 5.exd5 cxd5 shows White trading on h6 and leaving Black with doubled pawns and a clear disadvantage.

What the Hippopotamus Defense is about

After 1.e4 Nh6 Black develops the king's knight to the edge of the board. The idea is to keep the f-pawn free and build a flexible wall of pawns behind which the pieces gather, often with ...g6, a bishop on g7, ...d6 and ...e6. The knight on h6 can later go to f5, where it presses on d4.

The problem is speed and the center. The knight on h6 does not attack e4, so White can play d4 and Nc3 at no cost. White's c1 bishop can also go straight to h6 and trade itself for the knight, leaving Black with broken kingside pawns. The engine gives White a large edge after all three of its top replies, and across 280 games White scored 59.1%.

The main lines

There are no long, named variations here, but White has three good second moves.

2.Nc3 is the engine's first choice. After 2...c6 3.d4 d5 White trades with 4.Bxh6 gxh6 and opens the center with 5.exd5 cxd5. Black has a broken kingside and two isolated h-pawns.

2.Nf3 develops and waits. In the engine line 2...g6 3.d4 c6 4.Bf4 d5 5.Nc3 dxe4 Black gets ...g6 in first, so a quick trade on h6 is less damaging. White keeps a big center and better development instead.

2.d4 takes the center at once. The engine line 2...c6 3.Nc3 d5 4.exd5 cxd5 5.Bxh6 gxh6 again ends with White trading the bishop for the knight and leaving Black with weak pawns.

In all three lines Black's main counter is ...c6 and ...d5. That break is natural, but it opens the position while Black's kingside is still unfinished.

Typical plans for White

White's plan is simple: take the center, develop fast and look for the trade on h6.

• Center first. With e4 and d4, White controls the key squares, and Black has no immediate way to challenge them.
• The Bxh6 trade. If the h6 knight is still there after the c1 bishop is free, Bxh6 forces ...gxh6, splitting the kingside pawns.
• Open the center. After Black's ...c6 and ...d5, take with exd5 so the c-file and e-file open while Black is behind in development.
• Castle and use the extra space. Nf3, Bd3 or Be2 and short castling give a comfortable game.

Typical plans for Black

Black has to make the setup work despite the offside knight. The first step is ...g6 with a bishop on g7, so that Bxh6 can be met by a bishop recapture.

• Strike at the center. The ...c6 and ...d5 break is Black's main way to fight back.
• Use f5 for the knight. From h6 the knight can go to f5, hitting d4 and covering e7.
• Stay compact. A slow setup with ...d6, ...e6 and ...b6 can hold for a while, but White's space advantage grows if Black never breaks.

Black should accept that the position is worse and look for practical chances rather than a quick fight.

Mistakes club players make

• Black allowing Bxh6 without a reply. If ...gxh6 is forced and the king is still on e8, the kingside pawns are broken for good.
• Opening the center too soon. Playing ...d5 before finishing development often hands White open lines.
• White chasing the knight with pawns. Moves like g4 or f4 to hit the knight loosen White's own position. Simple development is stronger.
• White forgetting the trade. Many players develop the c1 bishop to f4 or g5 and miss the chance to take on h6 when it is strongest.

Who should play it

1...Nh6 is only for Black players who enjoy offbeat positions and play mostly fast games, where surprise matters more than the engine's verdict. Against well-prepared opponents it gives White a clear edge from the start.

If you like the Hippopotamus setup with ...g6, ...d6, ...e6 and ...b6, consider developing the knight to e7 or f6 instead, which keeps the same ideas without giving White the easy Bxh6 trade. For White, there is nothing special to learn: take the center, develop, and trade on h6 when it hurts Black's pawns. Once the center is secure, the extra space and the weak h-pawns give White an easy middlegame plan.

What the engine plays from here

Stockfish 17.1 at depth 20 rates the position +1.23: a clear edge for White. Its three top choices for White:

1. +1.23 2.Nc3 c6 3.d4 d5 4.Bxh6 gxh6
2. +1.21 2.Nf3 g6 3.d4 c6 4.Bf4 d5
3. +1.19 2.d4 c6 3.Nc3 d5 4.exd5 cxd5

Pawns, from White's side.

How it scores on lichess

280 rated lichess games reached this position; White scored 59.1%.

Light: White wins. Grey: draws. Dark: Black wins. About the sample.

How to play against it

As White, take the center with d4 and Nc3, develop the c1 bishop early and look for Bxh6 when it damages Black's pawns. Do not chase the h6 knight with pawn moves like g4 unless it wins something; simple development keeps a large edge.

Other lines with this name

The lichess opening list also files this line under the same name, though it reaches a different position: 1.e4 Nh6 2.d4 g6 3.c4 f6.

Questions

Updated October 2026. Sources and method.