Diemer-Duhm Gambit

The Diemer-Duhm Gambit departs from the usual French choices at move three. After 1. e4 e6 2. d4 d5, White neither defends, advances nor exchanges the e4-pawn. Instead 3. c4 adds a third pawn to the center and lets Black capture on e4. Unlike 3. Nc3 or 3. Nd2, the move develops nothing, so White's compensation has to come from central pawn mass and open lines. Opening literature regards it as dubious, and the engine gives Black a slight advantage.

Black accepts with 3...dxe4 in about three games out of five, which leads to the Diemer-Duhm Gambit Accepted. The main ways to decline are 3...c5, which strikes at d4 in the manner of the Franco-Sicilian, and 3...c6, which supports d5. Of the two, 3...c6 has given Black noticeably poorer results. The engine also lists the quiet 3...Nc6 and 3...h6 among its preferred replies. The gambit is rare at a serious level, but it appears fairly often in online play, and on Lichess the results for the two sides are close to even.