This move completes the Gambit.

...3.P to K Kt 4

This move has a double object. First, it protects the Gambit pawn, which would be attacked after White's necessary P to Q 4, and then it enables Black to post his B at Kt 2, which is essential, as in some variations White might play P to K R 4, when without the B at Kt 2, Black could not reply P to K R 3, because his Rook would not then be protected, and his pawns on the King's side would be broken up.

4.B to B 44.B to Kt 2
5.P to Q 45.P to Q 3
6.P to K R 46.P to K R 3

See previous remark. Of course, were Black now to advance the attacked pawn, he would weaken the Gambit pawn.

7.P takes P7.P takes P
8.R takes R8.B takes R
9.Q to Q 3...

The intention being to play P to K 5 and Q to R 7, attacking two pieces, and threatening mate. Black prevents this by—

...9.Kt to K R 3

White has not as yet gained any marked advantage to compensate for the sacrificed pawn.