Tarrasch Variation, Closed Variation

With 3...Nf6 Black puts a second attacker on e4 rather than striking at d4 with 3...c5, and the reply largely decides itself. Defending with 4. f3 fails, since 4...dxe4 also uncovers an attack on the unprotected d4-pawn. 4. e5 is therefore played in the vast majority of games. It gains space and drives the knight back to d7. The alternative 4. Bd3 is met by 4...c5 and transposes after 5. e5, while 5. c3 cxd4 6. cxd4 dxe4 7. Nxe4 Nxe4 8. Bxe4 Bb4+ gives Black equality. The engine gives White a slight edge.

After 4. e5 Nfd7, the usual course is 5. Bd3 c5 6. c3 Nc6 7. Ne2. The king's knight goes to e2 so that the d2-knight can use f3. Then 7...cxd4 8. cxd4 f6 9. exf6 Nxf6 10. Nf3 Bd6 frees Black's pieces, but the e6-pawn is left backward. White can instead hold on to e5 with 4. e5 Nfd7 5. c3 c5 6. f4 Nc6 7. Ndf3. This costs development time and gives Black dynamic chances if the position can be opened favorably.