to the
result--he makes as restricted as possible, _subject to two prime
conditions_. These conditions are:--

First, that there shall be room for the troops composing each corner
to be deployed--that is, spread out for fighting. Secondly, that there
shall be room between any two corners (A and C, for instance) for a
third corner (D, for instance) to move in between them and spread out
for fighting in support of them. He makes his square as close and
restricted as possible, because his success depends--as will be seen
in a moment--upon the rapidity with which any one corner can come up
in support of the others. But he leaves enough room for the full
numbers to spread out for fighting, because otherwise he loses in
efficiency; and he leaves room enough between any two squares for a
third one to come in, because the whole point of the formation is the
aid each corner can bring to the others.

In this posture he awaits the enemy.

That enemy will necessarily come on in a lengthy line, lengthy in
proportion to the number of his units. For it is essential to the
general commanding _superior_ numbers to make the _whole_ of the
superior numbers tell, and this can only be done if they march along
parallel roads, and these roads are sufficiently wide apart for the
various columns to have plenty of room to deploy--that is, to spread
out into a fighting line--when the shock comes.

[Illustration: Sketch 23.]

This extended line of Black marching thus against White strikes White
first upon some one corner of his square. Suppose that corner to be
corner A. Then the position when contact is established and the first
serious fighting begins is what you will observe in the above diagram.
A is the corner (now spread out for fighting) which gets the first
shock.

Note you (for this is the crucial point of the whole business) that
upon the exposed corner A will fall a very dangerous task indeed. A
will certainly be attacked by forces superior to itself. Normally
forces more than half as large again as A will be near enough to A to
concentrate upon him in the first shock. The odds will be at least as
much as five to three, the Black units, 4, 5, and 6, will be right on
A, and 3 and 7 will be near enough to come in as well in the first day
or two of the combat, while possibly 2 may have a look in as well.

A, thus tackled, has become what may be called "the _operative corner_
of the square." It is his task "to retreat and hold the