Petrov's Defense, Cochrane Gambit

The square f7 is read in algebraic notation as column f, row seven. In the Cochrane Gambit, White answers the attack on the knight by sacrificing it on f7. A gambit is a voluntary material offer made to obtain something else, usually time, activity, or access to the opposing king. The knight captures the f7-pawn, one of the pawns that protects the black king at the start of the game.

If the black king captures the knight, it leaves its starting square and loses the right to castle, meaning it can no longer use the special move that moves the king and one rook together. White tries to exploit this with a strong center, the bishop and queen entering the game quickly, and possible checks. That activity is called compensation: what a player receives for the material given up.

Compensation is not guaranteed recovery. White has surrendered a full piece and needs to open lines before Black coordinates the defense. Black should not cling to every unit of material if returning part of it helps the remaining pieces enter the game, moves the king to safety, and neutralizes the attack.