Two of Black's men are pinned, namely, the Knight f6 and the Pawn
e5, and of both pins White can take advantage.

The Pawn e5 is attacked twice and defended twice. White cannot
take Pawn, as he would lose Knight and Rook but would get for it
only Knight and Pawn. However, he can win the Pawn by playing (1)
P-d4. This attacks the Pawn for the third time and although Black
can defend him for the third time with R-e8, the defense is not
serviceable as Black would lose Pawn, Knight and Queen for Pawn,
Knight and Rook.

P-e4 in answer to P-d4 would not help either; for on e4 the Pawn
is twice attacked and only once protected as the Knight f6 cannot
be counted as protection on account of his being pinned by the
Bishop g5. All White needs to do is to take the Knight f6 first
and then to capture the Pawn e4.

It remains to examine whether in answer to (1) P-d4 Black can
take the Pawn with either Bishop or Knight. Apparently this is
possible as the Pawn d4 is protected only by the Knight f3 and
the Queen. Indeed, the combination would be correct if the Bishop
d7 were sufficiently protected. As it is White wins a piece in
the following way:

(1) P-d4 Bxd4
(2) Ktxd4 Ktxd4
(3) Qxd4 Pxd4
(4) Rxe7 Pxc3