course, swing the other way and disconcert him.

Black, therefore, has to keep his line even until he knows which way
White is going to swing.

[Illustration: Sketch 26.]

Let us suppose that White swings to the left.

Mark what follows. The distances which White's units have got to go
are comparatively small. B will be up at A's side, and so will D in a
short time after the swing is over, and when the swing is completed,
the position is after this fashion. Black's numbers, 1 to 9 inclusive,
find themselves tackled by all Black's twelve. There is a superiority
of number against Black on his right, White's left, and the remaining
part of Black's line (10 to 16 inclusive), is out in the cold.

If it were a tactical problem, and all this were taking place in a
small field, Black's left wing, 10-16, would, of course, come up at
once and redress the balance. But being a strategical problem, and
involving very large numbers and very great distances, Black's left
wing, 10-16, can do nothing of the kind. For Black's left wing, 10-16,
_cannot possibly get up in time_. Long before it has arrived on the
scene, White's 12 will have broken Black's 9 along Black's right wing.

[Illustration: Sketch 27.]

There are three elements which impose this delay upon Black's left
wing.