3. A clear field of fire, facilities for observation, a covered approach, concealment and cover for the guns and their detachments, and facilities for ammunition supply are advantages to be looked for in a good fire position, but one position will rarely unite them all. In arranging for the concealment of the guns it is important to consider the background. The neighbourhood of landmarks and the tops of prominent features should be avoided. 4. Their power of all-round traversing and their great effect against deep targets make machine guns specially suitable for position on a flank, whence they can bring enfilade fire to bear. A position in the firing line is rarely suitable, as the fire of the guns may be masked and the enemy’s fire drawn on the firing line. 5. The interval between guns in action should be as large as is compatible with effective control, but the front occupied by the massed guns of a brigade should rarely exceed 150 yards. _Machine Guns in Attack_ 1. Since machine guns are unsuited for maintaining a continuous fire, they will usually best assist the infantry by withholding their fire during the earlier stages of the battle, so as to be able to intervene at more critical periods. Machine guns allotted to a protective detachment will, however, always be employed so as best to assist the detachment in its special duties (_Field Service Regulations_, Part I., Chap. V.). 2. It will depend upon the general situation whether the machine guns should be placed under the control of the brigade machine-gun officer or left with the battalions to which they belong. When the facilities for concealment and control at effective range are good, and the brigade is engaged in a decisive attack, the best results will usually be obtained by unity of command. By a timely concentration of fire machine guns may thus be the deciding factor in the struggle for superiority of fire. When control is difficult, or when the brigade is extended over a wide front, it will usually be better to leave guns with their units. 3. It will often be advisable to employ both methods and to leave their machine guns with the battalions which are first extended, while those of reserve battalions are placed under the command of the brigade machine-gun officer. 4. Although machine guns can move with deployed infantry under fire, they should rarely attempt to keep pace with attacking infantry. When they have gained a position from which they can effectively support their infantry in the struggle for fire superiority and in the assault, they should only be moved for good and sufficient reasons. The difficulties of ranging and of concealment on the move usually outweigh the advantages of decreasing the range.