The Four Knights Game: Bb5 — A Level Fight for Black

This is a symmetrical double-kingside-pawn opening with both knights pinned. Neither side has claimed the centre with d4 yet, and both kings are still in the middle. Your main battle is simple: complete development without letting White exploit the pin on your knight. The most natural path is 5.O-O O-O, castling into safety and keeping the tension. If White plays 5.Bxc6, you need a plan for the doubled c-pawns you'll receive. If White plays 5.d3, you have a more closed, manoeuvring game ahead. The overriding principle here: do not rush. This opening rewards patience and piece play over cheap tactical tricks.

At depth 16, Stockfish recommends 5.O-O as White's best move. From there the main line continues 5...O-O 6.Bxc6 dxc6. You castle quickly, White trades bishop for knight, and you accept doubled c-pawns in exchange for the bishop pair and a semi-open d-file for your rook. This is the tabiya of the Four Knights, Bb5 variation. Black's position is fully sound — you have no weaknesses that can't be defended, and your two bishops can become powerful in the middlegame. The engine line shows that the most principled path leads to an equal game where your long-term compensation for the pawn structure is the two bishops and active piece play.

The Lichess database records over 1.5 million games from this exact position, which is a huge sample. White wins 49.8%, Black wins 44.8%, and draws make up 5.3%. Those numbers confirm the engine's verdict: this is not an opening where White is grinding you down — your winning chances are nearly as good as your opponent's. But notice the spread between White's best and worst options. White scores only 47.2% after 5.a3 and 46.3% after 5.d4 (which is a known mistake). So while the position starts level, a single inaccuracy from White can tip things your way. The drill will train you to recognise those moments.

According to the FACTS, 5.d4 is an inaccuracy that loses roughly 0.9 pawns of advantage compared to the better 5.O-O. This move tries to crack open the centre immediately while both knights are pinned, but it backfires because your pieces are well placed to meet it. After 5.d4, you can capture on d4 with tempo or simply maintain the tension — either way, you seize a lead in development. Because d4 is the fifth most popular move (25,819 games in the database), you will face it regularly at club level. Knowing how to handle it and grab your advantage is one of the highest-leverage things you can learn from this page.

The most-played continuation is 5.Bxc6, appearing in over half a million games. After 5.Bxc6 dxc6, you now have the bishop pair and a solid albeit doubled-pawn structure. Your immediate plans are straightforward: castle kingside (6.O-O or ...Bxc3 first are both possible), develop your dark-squared bishop to e6 or g4, and prepare to challenge the centre with ...f5 or ...Re8 and ...d6 depending on how White sets up. The doubled c-pawns look ugly but are actually hard for White to attack effectively. The important thing is not to waste time trying to undouble them — play actively with your bishops and rook along the d-file instead.