Chess Openings Lab
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Sicilian Defense: Paulsen-Basman Defense

The Paulsen-Basman Defense is 4...Bc5, where Black hits the d4 knight with the bishop right after the Open Sicilian trade. Black hopes for quick development and pressure on d4 and f2, while White wants to gain time on the bishop with Be3, Nb3 or Nb5.

Moves
1.e4 c5 2.Nf3 e6 3.d4 cxd4 4.Nxd4 Bc5
ECO
B40
Engine
+0.69 · a slight edge for White (Stockfish 17.1, depth 20)
Played
987 games in our lichess sample
White scores
49.3%

Key ideas for both sides

White

  • 5.Be3 defends d4 and offers a bishop trade; meet ...Qb6 with Na3, then Nb3 or Nc4 to chase the queen.
  • Retreat with Nb3 to attack the bishop, then Nc3 and Qd6 to use the dark squares Black left behind.
  • The 5.Nb5 jump eyes d6 and c7; after a trade on e3, the f-file opens for White's rook.

Black

  • Use ...Qb6 to add pressure on b2 and the d4 knight, forcing White to spend moves on defense.
  • After Nb3, drop the bishop to b6 and develop with ...Ne7 and ...O-O, keeping the dark squares covered.
  • Watch the d6 square: if White's queen arrives there, block with ...Bc7 and push it back.

Plans and pawn structure

Black's early bishop move starts a fight over the dark squares. White can gain time by hitting the bishop and steering it to b6, then aiming for Qd6 or Nb5-d6 into the hole left by ...e6 without ...d6. Black's plan is quick kingside development with ...Ne7 and ...O-O, then ...d5 to free the center. If White trades on e3 with fxe3, the f-file opens but the e3 pawn can become a target for ...Qb6.

Where the engine's main line heads: Open Sicilian: White traded the d-pawn for Black's c-pawn. An Open Sicilian: White traded the d-pawn for Black's c-pawn. White has a lead in development and the d-file, Black has the half-open c-file and two central pawns.

What the engine plays from here

Stockfish 17.1 at depth 20 rates the position +0.69: a slight edge for White. Its three top choices for White:

  1. +0.69 5.Be3 Qb6 6.Na3 Qa5+ 7.Bd2 Qd8
  2. +0.50 5.Nb5 Qb6 6.Be3 Bxe3 7.fxe3 Nf6
  3. +0.49 5.Nb3 Bb6 6.Nc3 Ne7 7.Qd6 Bc7

Pawns, from White's side.

How it scores on lichess

987 rated lichess games reached this position; White scored 49.3%.

under 120038.1%
1200–159949.8%
1600–199949.7%
2000 and up50.3%

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

How to play against it

As White, do not let the bishop sit on c5 for free. Play 5.Be3 and back it with Na3, or chase the bishop with Nb3 first. Avoid leaving b2 or f2 loose, because ...Qb6 can hit both at once. Once the bishop is pushed back, aim for Qd6 or a knight on d6.

Questions

What are the moves of the Sicilian Defense: Paulsen-Basman Defense?

The Sicilian Defense: Paulsen-Basman Defense starts 1.e4 c5 2.Nf3 e6 3.d4 cxd4 4.Nxd4 Bc5. Its ECO code is B40.

Is the Sicilian Defense: Paulsen-Basman Defense good for Black?

Stockfish 17.1 rates the position +0.69 at depth 20, which is a slight edge for White. In 987 lichess games from our sample, White scored 49.3%. A sneaky choice for Black players who like quick development, but it gives careful White players easy targets on the dark squares.

What is the main idea of the Sicilian Defense: Paulsen-Basman Defense?

Black develops the dark-squared bishop with tempo on the d4 knight. White answers by gaining time on that bishop and using the d6 square, which Black has left weak.

What should White play next?

The engine's first choice is Be3, with Nb5 and Nb3 close behind. 5.Be3 defends the knight, develops a piece and challenges Black's active bishop at once.

Updated October 2026. Sources and method.