TheLa variationvariant '''3... Nf6Cf6 4. Nf3Cf3 c5''' isés called theanomenada ''defensa Semi-Tarrasch Defense''. UnlikeA thediferència regularde l'habitual Tarrasch, Blackles doesnegres notno acceptaccepten antenir isolatedun pawnpeó aïllat, sinceja heque intendsvolen torecapturar recapture ona d5 withamb theel knightcavall (asja que després afterde 5.cxd5, 5...exd5 hasfa longmolt beende knowntemps toque bees dubiousconsidera afterdubtosa després de 6.Bg5Ag5), butperò he cedes acedeix l'[[ListGlossari ofde chesstermes termsd'escacs#SpaceEspai|spatialavantatge d'espai]] advantagea toles Whiteblanques. The intended recapture with the Nf6Cf6 prevents Black from seamlessly transposing to the Semi-Tarrasch if White has played 4. Bg5Ag5.
After 4...c5, White usually plays 5.cxd5 Nxd5 6.e3 or 6.e4, which lead to different types of middlegame play and have attracted the interest of strong players with both colours since the early twentieth century.
