Tarrasch Variation, Open System

With the knight on d2 blocking the queen's view of d4, Black challenges that pawn at once with 3...c5. The usual reply is 4. exd5. The older 4...exd5 frees the c8-bishop but typically saddles Black with an isolated queen's pawn after 5. Ngf3 Nc6, the Main Line. The Advance Line, 5...c4, gains queenside space instead. Today 4...Qxd5 is more popular, because White has no Nc3 to harass the queen. White usually gives up d4 temporarily and wins it back later. The Shaposhnikov Gambit, 4...Nf6, offers a pawn.

The Euwe-Keres Line, 4. Ngf3, readies the knight to take back on d4 and serves as a move-order tool. After 4...Nc6 5. exd5 Qxd5, White gains a tempo with 6. Bc4, so 5...exd5 is preferred, transposing to the Main Line. The Süchting Line, 4. c3, has the drawback that e4 still hangs. After 4...dxe4 5. Nxe4 cxd4 6. cxd4, White is the one left with a hard-to-defend isolated pawn. Black scores slightly better than White in online games after 4. c3. The engine considers 3...c5 roughly balanced.