Dummy trenches are laid out from aerial photographs, taken by aviators, and dummy advances are practiced with all the details as in real advances. Our information must be so complete that we know even where certain dugouts are in the enemy lines, and who occupies them. This knowledge comes from prisoners and deserters. Raids are put on to know what troops are opposing us by the identification of prisoners. Medical arrangements have to be completed so as to handle the hundreds or thousands of casualties that must occur. Immense guns must be brought up, and millions of shells must be piled along the roads and stored in dumps ready for use during battle. Water arrangements have to be made to supply pure water to the troops when they cross into enemy territory, for the enemy may have destroyed or poisoned the water supplies as they retired. Extra food rations and equipment must be supplied the men. Places of confinement for the hoped-for prisoners must be built. And, finally, thousands of extra troops must be brought up and trained for the attack. The above are only a few of the preparations that must be made, for the details are multitudinous. The most difficult thing is that these preparations must be carried out so far as possible without the enemy's knowledge. For he also has his aeroplane scouts taking photographs and looking about for information, his observation balloons and his spies, his raids and his prisoners. It is even possible that we might have a deserter who betrayed us to him, though one feels that this must be exceedingly rare. If the armchair critic has read the above he will perhaps realize a little more vividly than he has done before how difficult advances are and why it is more easy to talk of getting the enemy on the run than to actually do it. Once he has started to retreat and you to advance, your difficulties multiply and go on increasing in direct proportion to the distance that you get from your base of supplies. Your munitions, food and water must be transported from the rear over strange roads pulverized by shell fire, while your enemy is backing into greater supplies hourly. One of the most difficult propositions is to keep the different parts of your immense organization in communication with battalion, brigade, and divisional headquarters. Many different methods are used.