Chess Openings Lab
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Danish Gambit Accepted: Copenhagen Defense

The Copenhagen Defense in the Danish is 5...Bb4+, checking the white king right after Black has taken two pawns. White must block or move the king, and Black aims to trade the bishop on c3, play ...Nf6 and castle, keeping the extra material.

Moves
1.e4 e5 2.d4 exd4 3.c3 dxc3 4.Bc4 cxb2 5.Bxb2 Bb4+
ECO
C21
Engine
−0.53 · a slight edge for Black (Stockfish 17.1, depth 20)
Played
937 games in our lichess sample
White scores
56.8%

Key ideas for both sides

White

  • Block with 6.Nc3, the engine's choice, then Qb3 to hit the b4 bishop and f7 at the same time.
  • 6.Nd2 is quieter: Nf3 and short castling, accepting that Black keeps the pawns for now.
  • 6.Kf1 keeps both knights free but walks into ...Nf6 and ...d5 with the king stuck on f1.
  • After ...Bxc3+, recapture with the queen so it keeps an eye on g7 and the long diagonal.

Black

  • After 6.Nc3, play ...Nf6. If Qb3, take on c3 and castle at once.
  • Follow with ...Nc6 and ...d6 to cover e5 and keep the b2 bishop shut out.
  • Against 6.Kf1, ...Nf6 and ...d5 open the center against the misplaced king.
  • Trading the dark bishop for the c3 knight reduces White's attacking force and makes castling easier.

Plans and pawn structure

The check forces White to decide how to handle the b4 bishop. After 6.Nc3 Nf6 7.Qb3, Black trades on c3 and castles, and White's compensation rests on the b2 bishop and a quick Nf3. Black then wants ...Nc6, ...d6 and ...Qe7 to blunt the long diagonal. If White blocks with Nd2, the game is calmer and Black keeps two pawns. After Kf1, Black's ...d5 break comes with real force.

What the engine plays from here

Stockfish 17.1 at depth 20 rates the position −0.53: a slight edge for Black. Its three top choices for White:

  1. −0.53 6.Nc3 Nf6 7.Qb3 Bxc3+ 8.Qxc3 O-O
  2. −0.97 6.Nd2 Nf6 7.Nf3 O-O 8.O-O d6
  3. −1.03 6.Kf1 Nf6 7.e5 d5 8.exf6 dxc4

Pawns, from White's side.

How it scores on lichess

937 rated lichess games reached this position; White scored 56.8%.

under 120041.7%
1200–159959.7%
1600–199956.5%
2000 and up53.2%

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

How to play against it

As White, block with Nc3 and use Qb3 to make the check cost Black something. Avoid Kf1 unless you know the lines well. Keep your pieces active and aim at f7 and g7 before Black finishes ...d6 and ...Nc6. Every quiet move gives Black time to consolidate the extra pawns.

Questions

What are the moves of the Danish Gambit Accepted: Copenhagen Defense?

The Danish Gambit Accepted: Copenhagen Defense starts 1.e4 e5 2.d4 exd4 3.c3 dxc3 4.Bc4 cxb2 5.Bxb2 Bb4+. Its ECO code is C21.

Is the Danish Gambit Accepted: Copenhagen Defense good for Black?

Stockfish 17.1 rates the position −0.53 at depth 20, which is a slight edge for Black. In 937 lichess games from our sample, White scored 56.8%. A practical defense for Black players who want to trade attackers early; White needs Nc3 and Qb3 to keep enough pressure.

What is the main idea of the Danish Gambit Accepted: Copenhagen Defense?

Black checks on b4 to force White's reply, then trades the bishop on c3 and castles. Black aims to keep the two extra pawns and reduce White's attacking pieces before the Danish bishops can strike.

What should White play next?

The engine's first choice is Nc3, with Nd2 and Kf1 close behind. 6.Nc3 blocks with a developing move and prepares Qb3, which hits both the b4 bishop and f7.

Updated October 2026. Sources and method.