Dr Siegbert Tarrasch (1862–1934) – known for his often very dogmatic judgments – raised 3...c5 to the position of the only correct defence to the Queen’s Gambit. Anything else would lead to a cramped position, only 3...c5 would guarantee Black free development for his pieces. The price which Black has to pay in many variations for his active game is the isolation of his d-pawn, but the doctor and chess master Tarrasch valued the advantages of the isolated pawn even more than the disadvantages which were linked to it. As is the case in the Queen’s Gambit Accepted, positions with an isolated queen’s pawn are an important topic in the discussion of the Tarrasch and the Semi-Tarrasch. Central outposts for the knights, free diagonals for the bishops and open files for the rooks usually lead to lively games here.