_Carriers._--The carriers carry as many grenades as possible, and when their supply is exhausted they go to the reserve depots and replenish. They are responsible for a continuous supply of grenades to the throwers. _Barricaders._--The barricaders are charged with the construction of barricades. They carry sandbags and tools for filling them. In addition they carry as many grenades as possible. They hold themselves in readiness to go forward and construct a barricade or cover at any point designated by the squad leader. [Illustration: PLATE 41 _Combat in a Communicating Trench_] _General._--All the men of the squad must be trained and prepared to take over the duties of any other member. Before undertaking any operation each man of the squad should thoroughly understand the part he is to play in it. _Formation._--The formation for the several classes of tactical employment will be explained when each is considered below. OFFENSIVE OPERATIONS When it has been decided to attack a certain sector of the enemy's position a detailed reconnaissance is made with a view to locating and developing every element of the position, detailed plans are made and imparted to all concerned. (See Chapter XI.) The phases of the attack consist of: (1) The artillery preparation; (2) the infantry assault; (3) the occupation and organization of the captured position, and preparation to meet a counter attack. During the course of the artillery preparation grenadier squads work their way across "no man's land" and establish themselves sufficiently close to throw grenades into the fire trenches. Failing in this they accompany the assaulting troops. When they are able to work up close they cover the advance of the infantry assaulting lines by showering grenades into the enemy's fire trenches after the curtain of artillery fire has been extended back into his position to prevent the supports and reserves from coming up to the front. All men of the squad carry as many grenades as possible and such number as the squad leader may designate act as throwers, while the others act as carriers and prepare the grenades for throwing. Accurate throwing, properly observed and distributed, will greatly assist in preparing for a successful assault. CLEARING FIRE TRENCHES No matter how well the infantry assault on the enemy's fire trenches may be conducted, it rarely succeeds in occupying the hostile position throughout its entire length. Casualties, loss of direction, and unexpected obstacles encountered are bound to break up the assaulting line more or less, thereby leaving gaps in the captured position. Furthermore the attack on a line of trenches takes place on a relatively small front by a large number of men. When the trenches are finally reached and a lodgment effected there will be great overcrowding. Provision must be made immediately for extending the line, otherwise the casualties at these points will be exceedingly heavy.