Machine guns must be used on the principles given above, which naturally fall under two distinct headings, viz. use by day and use by night. Machine guns with outposts by day will not occupy their fire positions unless an attack is imminent, but should be posted with the reserves in their own section of the defence. This must not prevent emplacements or pits for the guns being made, ranges carefully taken and written up, and everything being ready in case of action. These positions and the subsequent action will correspond so closely with those already suggested for infantry in the defence in the last chapter, that they need not be repeated. By night, however, the case is very different, and it is necessary to select very carefully the position of each gun, so that it commands a road, a bridge, or other ground which the enemy in advancing may be compelled to pass or occupy. These places must be selected in order of importance, and an endeavour made to leave no approach by which a body of troops might move uncovered by fire. The machine guns must occupy their positions before dark and be carefully laid to sweep the area of ground necessary for protecting the position, the angle of elevation of the gun being taken by clinometer afterwards in order that it may be relaid if necessary in the dark. Great care must be taken to conceal these guns from observation when bringing them into position or withdrawing them, and it is worth while going to some considerable trouble to do this. One method of many is suggested to show what is meant. Field guns might be placed in the positions by day and withdrawn before night, the machine guns being brought up on the limbers and dropped in the position behind a screen of brushwood, and withdrawn again in the morning when the field gun is brought up. The detachment of each machine gun must find two double sentries and their reliefs, who will remain at their posts with the gun, which should have the belt ready in the feed block, but not actually loaded. These men may either take it in turn to stand to the gun or both be directed to watch. When there are no infantry sentries on piquet duty in front of the gun, it will be necessary to detail two who will be posted in the usual way some little distance in front of the gun to prevent it being rushed in the dark. The method of preparing the sights and laying the gun for night work is given in Chapter VII. The value of machine guns with the outposts at night is shown by an incident at the Battle of Mukden, March 6th, 1905. Two Russian battalions made a night attack against the hill north of Tung-chia-wen, which was occupied by the 2nd Japanese Regiment. There was no moon and the night was very dark. Two Japanese machine guns did great execution at ranges between 50 and 100 yards, and the Russians were repulsed with a loss of 450 men, the Japanese casualties being only 48. CHAPTER VII EMPLOYMENT IN FORTRESS WARFARE