Coast Artillery: (1) Permanent fortifications for defense against naval attack. (2) Semi-permanent fortifications for protection of permanent from raiders. (3) Organization of mobile troops to prevent landing of enemy. MILITARY INFORMATION. Essential: (1) To enable War Department to estimate equipment and size of force necessary. (2) To enable commander properly to estimate the situation in the field of operations. TRANSMISSION OF INFORMATION. Wire, Signaling, Radio and Messenger: Message.--Concise, written information sent by messenger or wire. Source always given.--"Heard" separated from "seen." Report.--Formal account of some enterprise. War Diary.--Record of events kept in campaigns. Maps. Reconnaissance: The work of individuals or units in gathering information. To keep contact with the enemy--to be acquainted with the terrain; to protect flanks and rear and guard against surprise. Reconnaissance begins on entering theater of operations and lasts through campaign. Effected by patrols and air craft. Indications of enemy: Tracks on road. Abandoned camps and clothing. Infantry, thick, low cloud of dust. Cavalry, high, thin cloud of dust. Artillery and wagons, broken cloud. Determination of Enemy Forces: Timing past a given point. Cavalry (walk), 110 per minute. Cavalry (trot), 200 per minute. Infantry, 175 per minute. Artillery and wagons, 5 per minute. Security: Those measures taken to protect a command from enemy observation, annoyance and surprise. Obtained by covering the front with detachments. March.--Advance, flank and rear guards. Camp.--Outposts. March and camp detachments.--To give warning and resist attack until such time as detachment in rear can deploy. Advance Guard: Detachment from main body to cover its advance. Against surprise for information. Push back small bodies. Check enemy's advance until deployment in rear. Seize good position and locate enemy lines. Remove obstacles. Strength 1-20 to 1-3 of entire command. Divisions of Advance Guard: Cavalry point. Infantry point. Advance party. Support. Reserve. Leading Troops: A detachment protecting the head of a column in retreat. Rear Guard: Detachments protecting the rear of a retreating column. Formation like that of advance guard. Flank Patrols: Detachments for protecting the flanks of marching column. March Outpost: Detachments for protection of column halted on march. Formation, that of the marching protection. Outpost: The detachments forming the protection for a force in camp or bivouac. Divisions of Outpost: Reserve. Line of supports. Line of outguards. Pickets. Sentinel Posts: Sentry squads. Cossack posts. Sentinels. Detached posts (from support). Hours of Special Danger: Evening and dawn; thus good times to relieve outposts.