I. Relief in the Trenches.

A. THE TWO MAIN CLa.s.sES OF RELIEF: 1. General Relief. Applied to the relief of a whole position manned by a division or more. Executed when large units are going to "full rest" in the rear or being removed from one part of the front to another. Executed in the same way as interior relief; i.e., by successive relief of the battalions involved.

2. Interior Relief. Applied to the relief of one sector or portion of a sector manned by a brigade or less.

B. GENERAL PRINCIPLES OF RELIEF:

1. Interior relief is executed about once every six days; more frequently when the stay in the trenches is particularly arduous, less frequently when it is unusually comfortable.

2. The battalion is the relieving unit.

3. It is advisable to arrange the relief between units which have friendly relations to one another; e.g., battalions of the same regiment; and, so far as possible, to a.s.sign each unit to the same trenches on each relief. This promotes continuity of effort.

4. Relief is executed at night; the hour must be varied; secrecy is imperative.

5. Prompt execution is essential, to prevent fatigue of the troops and congestion of the boyaux.

C. THE MECHANISM OF RELIEF:

1. Reconnaissance, 24 hours in advance, by the captain of each relieving company, accompanied by his platoon leaders and non-commissioned officers. He ascertains: (1) The plan of occupation; i.e., the dispositions and duties of the unit to be relieved.

(2) The shelter accommodations.

(3) Work being done and proposed.

(4) Condition of the wire and other defences.

(5) The available water supply.

(6) Artillery support.

(7) Communications.

(8) The location, amount and condition of stores.

(9) Danger points.

(10) All available information of the enemy; his habits, location of his snipers, what work he is doing.

(11) The ways and means of liaison, both lateral and from front to rear.

To the success of this reconnaissance, the closest co-operation between all officers of the companies relieving and relieved, is indispensable.

2. The march from billets to the trenches: (a) Transportation, by auto-trucks and wagons, is utilized to a point as near the lines as possible, to carry the packs of the men, the auto rifles, extra ammunition and other heavy equipment. When the distance is great the men themselves should be carried by auto-truck; this saves time and fatigue. The men will carry rifles loaded and locked, full cartridge belts, gas masks, and all other lighter equipment, with rations for 24 hours at least. Grenades will be secured in the trenches.

Electric torches will be carried by company and platoon commanders.

(b) The strictest discipline must be maintained. On arrival within sight of the enemy, noise and smoking (or other lights) will be prohibited.

(c) Guides, from the company to be relieved, will meet the relieving company promptly at a point definitely agreed upon in advance.

3. The march through the boyaux (communicating trenches): (a) Distance; often as much three or four miles.

(b) Order of march: company in single file, captain at the head; each platoon leader at the head of his platoon; a non-commissioned officer at rear of each platoon.

(c) The column must be kept closed up. Each man must consider himself a connecting file, guiding on the head, and behave accordingly. A guide should accompany the commander of the last platoon.

(d) Rate of march: roughly, about 40 yards per minute. It takes 250 men about 20 minutes to pa.s.s a given point.

(e) Route and right of way: The first line and support trenches will never be used as roads. Separate boyaux should, if possible, be a.s.signed to the troops relieving and relieved. In no case will one company cross the path of another. In case of two columns meeting, one moving forward, the other to the rear, the former has the right of way.

4. No man of the unit in occupation will leave his post until he has actually been relieved and has transmitted all orders and information relative to that post.

5. Liaison must be established, immediately on arrival, with the units on the flanks and with headquarters in the rear.

Captains must make sure that their runners are thoroughly acquainted with the routes of communication.

6. As soon as relief is accomplished both captains will report that fact to their respective commanders.

7. The relieving commander then inspects his trenches. He ascertains that all his watchers are at their posts and that the balance of his men know their posts and duties and are prepared to a.s.sume them quickly.

8. The duties of the relieved commander are: (1) To turn over his sector thoroughly policed and in good condition as regards its construction and the new work, if any, in progress.

(2) To turn over his supplies in good condition and fully accounted for.

(3) After reporting the relief, to march his men back to billets as promptly and secretly as possible, in column of files, platoon leaders in the rear of their platoons, a non-commissioned officer and guide at the head of each.

(4) On the evening preceding relief, to send his cooks back to billets so that his men may be provided with a hot meal immediately on arrival.

D. If an attack occurs during the march through the boyaux, to or from relief, the company affected occupies the nearest defensive position and at once notifies its battalion commander. If an attack occurs during the actual process of relief, the senior officer present takes command.

II. The Stay in the Trenches.

A. THE FOUR OBJECTS OF A TRENCH COMMANDER:

1. Security of his sector.

2. Protection of his troops.

3. Constant and accurate observation.

4. A continuous offensive.

B. HIS PLAN OF DEFENSE:

1. General principles of defense: (a) Arrangement in depth. The most dependable defense is in prearranged counter attacks. The system of defense must react like a helical spring.

(b) Tenacity of defense.

1. Each unit must be prepared to hold its post to the last extremity.

2. Orders to withdraw will never be obeyed unless unmistakably valid.

3. All ground lost must be retaken at once in counter attack by the unit which lost it.

(c) Apportionment of responsibility. Each active segment must have a commander responsible for its defense, upkeep and sanitation, and the discipline and instruction of his men.

2. Basis: (a) The plan of defense turned over by the preceding commander.

This will usually suffice for the first 24 hours after relief.

(b) General information of the enemy's lines, dispositions, and intentions, based chiefly on aerial photographs.

C. ORGANIZATION OF DEFENSE:

1. Allocation of front. (The front of an American battalion will average about 1,000 yards.) Diagrams: A. The Regiment. B. The Battalion. C. The Company. D.

The Platoon.

2. Distribution of effectives. Determined chiefly by the terrain and by 3.

3. Employment of the several arms: (a) Machine guns. Crew of 8 men per gun. (Furnished by detachments of a machine gun company.) Located by the infantry commander, in concealed emplacements behind the first line, to deliver successive barrages from flanking positions. Effective range: up to 700 yards.

(b) Automatic rifles. Crew of 3 men per rifle. Usually posted to enfilade the entanglements of the first line. They concentrate the fire effect of from 7 to 10 riflemen.

Effective range: up to 300 yards.

(c) Rifle Grenadiers. Located near enough to first line to hold the enemy trenches under fire and deliver effective barrages near the mouths of our own communicating trenches. Should be located near observation posts so that their fire can be promptly corrected.

(d) Trench mortars. Located similarly to (c). Manned by riflemen.

(e) Bombers. One supply man to each 2 grenadiers. Used for protection of auto-rifles, in counter attacks, for protection of communicating trenches and fighting in close quarters.

(f) Riflemen. Posted to deliver frontal fire. Grouped according to the plan of counter attacks.

(g) As many men as possible should be instructed in the use of the enemy's weapons.

D. LIAISON:

(a) By telephone. Quickest and most accurate. Maintained between each platoon and its company headquarters, and between adjoining companies. Especially subject to destruction in bombardment. Wireless and ground telegraphy are used only between brigade and division headquarters.

(b) By runners ("liaison agents"). Five detailed from each company to battalion headquarters; one sent to each adjoining company headquarters; one from each platoon to company headquarters; four or five on duty at each platoon headquarters; five from each machine gun company to battalion headquarters. Messages sent by them should, if practicable, be written and signed, and should be receipted for by the addressee.

(c) By rockets and flares. Quickest means of liaison with the artillery in rear.

(d) Domestic (message carrying) grenades.