Up to this move an even exchange of pieces has taken place, but
now Black loses the Bishop which is attacked by White's Rook,
because White can remove the Knight which protects the Bishop.

(5) Bxf6 Pxf6
(6) Rxd7, etc.

Instead of playing (1) P-d4 and taking advantage of the fact that
the Pawn e5 is pinned, White can direct his attack against the
other Black man which is pinned, namely the Knight f6. He can
play (1) Kt-d5 and thereby attack the Queen and at the same time
the Knight f6 for the second time. It will not be evident to the
beginner that White can derive any advantage from this double
attack, as Black can answer either Q-d6 or Q-d8 keeping his
Knight twice protected. Indeed, White does not gain anything on
f6, the square itself upon which the pin is effected, but he uses
the pin to force an opening into the chain of Pawns which
protects Black's King by exchanging on f6, compelling Black to
retake with the Pawn g7. The advantage resulting from this break
in Black's Pawn position will be explained later on when
discussing the strategy of the middle-game.



SACRIFICING



A player is said to SACRIFICE if he allows a certain amount of
his forces to be captured without recapturing himself an