It may be possible, and advantageous, to move forward a proportion of the guns with the attacking lines of the infantry. The guns allotted to this duty will not take part in the covering fire, but will keep themselves fresh and their ammunition intact, in readiness for the advance. Their duties will be to:— (_a_) Help the infantry to gain fire superiority at the decisive point. (_b_) Make good and hold positions won. (_c_) Pursue the enemy by fire. (_d_) Watch for and repel counterattacks. (_e_) Enable the infantry to re-organize. As enemy snipers are a particular source of annoyance to machine gunners, they should be watched for. The defence of prepared positions has been already dealt with under the heading of Machine Guns in Trenches. Machine guns in any defensive position must be so organized that they can support each other mutually throughout any given section of the defensive line. It must be remembered that the best positions for machine guns are not always the same by night and day. It will often be necessary to move the guns from the night position to the day position before dawn. =Rearguard Action.=—The following points must be considered:— A wide field of fire. Guns must be carefully concealed in the least obvious places. Covered lines of retreat must be carefully reconnoitred. Limbers must be close up, to facilitate hasty retirement. Positions in rear must be chosen before the guns leave the position they are holding. A proportion of the guns should occupy the position in rear, before all guns retire from the forward position, thus the retirement of the last guns can be covered. =Village Fighting.=—As soon as the infantry have made good one edge of the village, the guns will be brought up as close to the firing-line as possible. They will then search windows, doorways, roofs, etc., likely to be held by the enemy. Guns will be used to command cross-streets, etc., so as to guard against attacks on the flanks or rear of the infantry. Guns should also be posted on the edges of the village, to prevent flank attacks. During village fighting every use should be made of windows, doors, etc., as machine gun positions (see page 102). =Co-operation.=—The necessity for co-operation between the machine guns taking part in any particular action cannot be overestimated. Not only should the individual gun of a particular unit work upon some definite plan for mutual support, but the sections of all units that are operating together should co-operate with a view to obtaining the best results from their combined action. This cannot be done in action unless it has been previously practised. Therefore great attention should be paid to training a number of guns to operate together for some specific purpose.