(ii) =Cavalry.=--The fire effect which infantry can develop against cavalry is such that infantry which is ready to open a steady and timely fire has nothing to fear from a cavalry charge, provided the cavalry cannot find dead ground over which to approach. Any formation which allows fire to be delivered quickly and accurately is suitable for meeting cavalry. Closing an extended line to meet cavalry delays the opening of fire, and may offer a vulnerable target to the enemy’s artillery. Even if cavalry succeeds in riding through a firing-line, it can inflict little loss upon it if the infantry holds its ground. Whenever there is a possibility of being charged by cavalry, special care must be taken to watch and guard the flanks. (iii) =Artillery.=--Artillery coming into action, limbering up, or in movement, is a vulnerable target against which rapid fire or even fire at long infantry ranges is justifiable. Infantry will experience difficulty in putting shielded artillery out of action by _direct fire_ even at close infantry ranges, but it can prevent the artillery from moving and interfere with the service of the guns. Infantry can best obtain decisive effect against guns with shields by means of _enfilade or oblique fire_. (iv) =Machine-Guns.=--Machine-gun sections with their guns on travelling carriages are as vulnerable as artillery limbered up; but detachments carrying the gun into action are difficult to distinguish from infantry. Machine-guns in position _are usually concealed_, and are a difficult target. To obtain good effect against them it is usually necessary to employ a considerable number of rifles. (v) =Aircraft.=--Aircraft form a very difficult target to fire directed from the ground, and only a small proportion of their area is vulnerable. Bullets can pass through the fabric of aeroplane wings without doing serious damage. Indiscriminate fire at hostile aircraft is, moreover, likely to cause casualties in neighbouring units, and will also disclose the position of the troops to the enemy’s observer. The strictest control must be exercised over all fire directed against aircraft. In the case of rifle fire at _aeroplanes_, men should be instructed to aim _six times the length of the machine in front_, and _at the nose of the envelope in the case of airships_. (vi) =Retiring Troops.=--Other conditions being equal, the effect of fire in the open at all ranges is always greater when directed at retiring troops as compared with the effect on troops advancing. Section =44=.--Tactical Application of Rifle Fire.