Marshall Defense

The Marshall Defense answers 2. c4 with 2...Nf6, guarding d5 with the knight instead of a pawn. Wikipedia lists it among the second moves that decline the gambit without ...e6, and it is handled separately from the 2...e6 main line. The position can also arise by the move order 1. d4 Nf6 2. c4 d5. By omitting both ...e6 and ...c6, Black keeps the c8-bishop's diagonal open and sidesteps the problem piece that defines the Queen's Gambit Declined proper.

The cost is that d5 lacks pawn support. After 3. cxd5 Black has no pawn recapture available. If the knight takes back on d5, it stands exposed in the center, where White can later attack it and gain a tempo. For this reason the defense is seldom adopted at the higher levels. The engine gives White a slight edge and prefers 3. cxd5, with 3. Nf3 and 3. Nc3 close behind.

In practice 3. Nc3 is the most common reply, chosen in roughly half of all games. It develops a piece and adds pressure to d5 without committing the c-pawn. 3. cxd5 is the second most frequent choice and gives White the best results of the three main moves. 3. Nf3 is the third option. Across all games White scores somewhat better than Black. The position is reached often in online play and ranks among the more frequently seen named openings on Lichess.

The Tan Gambit, 3. cxd5 c6, is Black's way of avoiding a passive recapture. White is best advised to accept the pawn. After 4. dxc6 Nxc6 Black is a pawn down but leads in development, which offers at least partial compensation. In the middlegames that follow, White usually holds a small advantage, yet Black's position tends to stay defensible. Even in endgames the extra pawn does not guarantee White a win, and Black retains drawing chances.