y scouts, special attention being paid to roads and tracks
parallel with the advance. This screen is followed by the remainder of
the Vanguard, in collected formation, until it is in contact with or in
the vicinity of the enemy, with protection at all times against local
surprise. The Main Guard follows, in touch with the Vanguard, and with
local protection. Both portions have definite commanders, and the
commander of the whole Advanced Guard will probably move with the
supports of the Vanguard. The commander will also determine the
_relative distances_ between the Vanguard and the Main Guard, these
being regulated by the strength of the Advanced Guard, and being based
upon the necessity of one part supporting the other. The distance of
the {107} Advanced Guard ahead of the Main Body may have been mentioned
in the operation orders, but if it is left to the discretion of the
Advanced Guard commander he will be guided solely by the interests of
the force he is covering, and his decision will be influenced by the
nature of the country (whether it is open, or intersected by woods,
hedges, sunken roads, etc., which make observation even by aircraft a
matter of great difficulty) and by the tactical situation, such
distance being chosen as will suit these conditions, while admitting
the fulfilment of the objects in view, viz.:--to obtain information
concerning the enemy and to prevent hostile reconnaissance; to prevent
surprise and delay; and to enable the Main Body to deploy into battle
formation without interruption by the enemy's fire.

It is also the duty of the commander to ensure _communication_ between
the various parts of the Advanced Guard and between that force and the
Main Body, by arranging for mounted orderlies and cyclists, signallers
and connecting files, in addition to the contact patrols furnished by
the Air Service, and to such telegraphic and telephonic communication
as can be provided in the field by the Signals. This is of the first
importance, as the action of the commanders of the Advanced Guard and
of the Main Body will depend on information received, and not only must
information be gained by every available means, but it must also be
communicated without delay to all concerned while it is fresh and
before it becomes stale. It must also be remembered that negative
information (_e.g._ that such and such a village has been thoroughly
searched and no trace of the enemy found) is at least of equal va