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 discipline must be maintained, so that there is the strictest compliance with verbal orders and signals, and application on the battlefield of the habits inculcated during the training period. The time when fire is to be opened is often left to the discretion of the fire-unit commander, but, generally speaking, fire should be opened by an {38} attacking force only when a further advance without opening fire is impossible; and even in defence, when access to the ammunition reserve is likely to be far easier than in an attack, withholding fire until close range is reached is generally more effective than opening at a longer range. The tactical value of a withering fire at close range from a hitherto passive defender has again and again been proved in battle. On the _Heights of Abraham_ (September 13, 1759) General Wolfe had assembled his troops and he awaited Montcalm's attack. Not a shot was fired by the defenders until the attacking force was within forty paces, and three minutes later a bayonet charge into the broken foe swept the French helplessly before it. At the _Battle of Bunker