During siege operations (as in Europe, where some trenches have remained in about the same place for long periods) photographers go up in airplanes each morning and photograph the enemy's trench lines. Blue prints are made of these lines. By comparing these with the lines of the previous day it is easy to determine the changes that have been made during the night. Other airplanes are detailed for the purpose of combat. They prevent opposing airplanes from gathering information. THE BIG IDEAS OF MARCHES For marches to be entirely successful three conditions must be fulfilled: (1) the troops must get there; (2) they must get there on time; (3) and they must get there in good condition. Now suppose that you were ordered to conduct the march of a company of green men for a distance of 200 miles, just how would you solve the problem? Before starting, very careful preparations should be made. Your men should be in good physical condition; they must be given so much work that they are athletes. Keep these points in mind: 1. Always have, when possible, the comfort of your men in mind. Their work in carrying a load of nearly forty pounds and marching around fifteen miles a day will be hard enough. Don't give them any extra hardships. 2. Make the conditions of the march pleasant. Encourage the men to laugh and sing. 3. Use wagons, automobiles, etc., to carry heavy loads (burdens) whenever possible. 4. It is a custom of the service to help a man who may not be strong physically but who is straining every nerve to get there. Be the first to volunteer to carry for him his rifle or part of his burden. 5. Look out especially for the feet of your men and the hoofs of your animals. 6. On long marches one day in seven should be a day of rest and recreation. 7. Never take an extremely hard and long (forced) march unless imperative. 8. As a rule troops pay no compliments on the march. They have enough to do without that. 9. Let the object to be accomplished determine the general conduct of the march (the time of starting, the rate, length of march, halts, etc.) SHELTER When troops are sheltered under canvas (in tents), they are in camp. When they are resting on the ground without tents (for instance, on the firing line the night before or during a battle), they are in what is called bivouac. When they occupy buildings in towns or villages, or huts especially erected, they are in cantonment. When they are assigned to public (such as post-offices, town halls, court houses, hotels, etc.) or private buildings they are said to be billeted. SELECTION OF A CAMPING GROUND Suppose that you were sent on ahead of troops on the march to select a camp ground for them, what big ideas should you bear in mind. 1. The ground should be large enough for the troops without crowding. In case of rain it should be easily drained. And there should be no stagnant water near (say, within 300 yards). 2. There should be plenty of pure water.