Marshall Variation (with 4.Nf3 Bg4)

The idea

After 3.d4 Nxd5 4.Nf3 Bg4, Black has the pawn back and the bishop out actively, pinning the knight on f3. Lichess calls 3...Nxd5 the Marshall Variation and 4.Nf3 Bg4 its Gipslis Variation. White's other main try is 4.c4, chasing the knight.

Plans for White

Develop with Be2, castle, and gain space with c4 to push the knight away. h3 asks the bishop to decide. White's extra central pawn and space are the long-term assets.

Plans for Black

Develop with ...e6, ...Nc6 or ...Nd7, ...Be7 and castle. If White plays c4, the knight drops back to b6 or f6. Black wants to pressure d4 and to trade the bishop on f3 when that weakens White's structure.

Watch out for

For Black, the knight on d5 after c4. It must have a good retreat, and moving it again costs time. Tartakower called 4...Nf6 the soundest reply to 4.c4.

For White, the pin. With the bishop on g4, the knight on f3 can't defend d4 freely, so the d4 pawn can come under pressure from ...Nc6 and ...e6.