Tarrasch Variation, Guimard Defense

The Guimard Defense, also called the Guimard Variation, answers 3. Nd2 with 3...Nc6, bringing a piece out at once and adding pressure to d4 instead of challenging the center with a pawn. The drawback is structural: the knight stands in front of the c-pawn, so the ...c5 lever that normally defines Black's counterplay in the French is unavailable. In the main line, 4. Ngf3 Nf6 5. e5 Nd7, Black turns instead to ...f6 to remove the cramping e5-pawn, but without ...c5 there is little pressure on d4, and White keeps a slight plus with 6. Be2 or 6. Nb3. Engines also consider 4. Bb5, pinning the knight.

The second most common reply, 4. c3, shores up d4 in advance. Black can then release the tension with 4...dxe4 5. Nxe4 e5, the Thunderbunny Variation, using the knight on c6 to back a central counterstrike. The exchange 4. exd5 is a minor option. The engine gives White a slight edge after 3...Nc6, though in online play the results are nearly even. The line remains a rare sideline rather than a main defense.