Distribution in depth is necessary during the preparatory stage of the fight, as it enables the commander to meet unexpected developments in the situation. Moreover, it is justifiable so long as the information in regard to the strength and intentions of the enemy is insufficient. When reconnaissance work is not thoroughly performed, the force may be obliged to deploy in a direction other than the one originally chosen. This will be difficult to do as changes of front and movements by the flank can only be made when the front is narrow. Moreover, after a force is once deployed within the zone of hostile fire, it is committed to the direction chosen and can only move straight to the front. Considerable changes of front can only be executed by the lines in rear. The troops held in rear are to reinforce the firing line and to increase its density to the maximum at the decisive moment. As the losses are smaller in defense than in attack, a force can cover a broader front and keep its supports in closer proximity to the firing line in the former than in the latter case, especially if it was able to strengthen its position. The reserve, however, should be kept at a greater distance from the firing line than in attack, in order that it may retain complete freedom of movement--in covering the retreat, or in making a counter-attack--and may not be involved in the fire fight. The reserves of the attacker are to protect the flanks, give the impetus for the assault, serve as a force upon which the attacking line can rally, and cover the re-forming of the troops after a successful attack. The several echelons of the attack formation, except the small fractions immediately supporting the firing line[233] and covering its flanks, should have become merged with that line by the time the decisive moment of the combat arrives. The commander who takes up an unnecessarily deep attack formation dispenses with an advantage; on the other hand, the one who prematurely deploys in force, exposes himself to grave danger. _The troops should be sent into action in a deep combat formation, since the firing line is to be fed from the rear until the decisive moment arrives, but every available man should be thrown in for the assault._ [233] The advantage of having such supporting forces in rear of the line is clearly shown in the fights of the 18th Brigade at Wörth. KUNZ, _Kriegsgeschichtliche Beispiele_, 14, pp. 110, 129 and 172.