on must be communicated at once. By
intelligent observation superintending commanders can co-operate with
one another, can anticipate situations as they develop, and decide at
the time what steps will be necessary to meet them. A general
reconnaissance will be in progress during every modern battle by
observers in aircraft and in observation balloons. In addition, local
reconnaissance by means of patrols and scouts will usually discover an
opening that might otherwise be lost, and may warn a commander of an
intended movement against him, which might otherwise develop into a
disagreeable surprise.

Co-operation and Mutual Support were developed in their highest form by
the Allied Corps Commanders in the _First Battle of the Marne_
(August-September, 1914). {37} In this campaign close on 1,500,000
troops were engaged on both sides, and the Corps Commanders,
particularly those of the French VI. Army (Manoury), III. Army
(Sarrail), and the Military Governor of Paris (Gallieni), were
continuously in touch with one another, and frequently rendered
assistance, unasked, by fire and by movement. Co-operation of a novel
kind was exhibited on a minor scale during the First Battle of the
Somme. An attack was launched on _Gueudecourt_ (September 26, 1916) by
the 21st Division, and a protecting trench was captured as a
preliminary to the larger movement. A tank, followed up by infantry
bombers, proceeded along the parapet of the trench firing its machine
guns, while an aeroplane swooped over the trench firing its Lewis guns.
The survivors in the trench surrendered, and the garrison was collected
by supporting infantry, who advanced in response to signals from the
aeroplane.

FIRE TACTICS.--It has already been noted that the battle is the only
argument of war; it is also the final test of training, and on the
battlefield no part of the syllabus is more severely tested than that
devoted to _musketry_. The fire tactics of an army, its combination of
fire and movement, the direction and control by the leaders and the
fire discipline of the rank and file, make for success or failure on
the field of battle. The fire must be directed by the fire unit
commander against an objective chosen with intelligence and accurately
defined; it must be controlled by the sub-unit commander, who must be
able to recognise the objectives indicated, to regulate the rate of
fire, and to keep touch with the state of the ammunition supply. Fire
dis