Intended to frustrate that manoeuvre, the British attack compelled the German commanders to await, before they could make any such attempt, the arrival of reinforcements. On both sides there was now a race against time. French reinforcements and reserves had to be brought up and massed against the flank of the German position. Many of those troops had, however, to cover long distances afoot. The movements of mass armies are comparatively slow. After all, the roads and railways traversing a country have a capacity which is limited. Some idea of what such movement involves may be formed from the traffic on a popular bank holiday. In the case of armies there is, in addition to human numbers, the artillery, the munitions, the camp equipment, the foodstuffs, and all the rest of the transport. No one, therefore, can be surprised that by the time these masses could be concentrated on the German flank, there were German masses who, under the same conditions, had been hurried forward to meet them. From the very necessities of time and space the race resulted to a great extent in a draw. The Battle of the Aisne is in every respect unique. A battle in the ordinary sense of field operations it was not. It was a siege. Nothing at all like it had ever occurred before in war. There have been many sieges of banditti in mountain retreats. There have been sieges in old times of fortified camps. There had never been the siege under such conditions of a great army. The operations in this amazing and gigantic conflict, though inter-related, must for the purposes of clear narration be dealt with in sections. The story divides itself into:-- The attack upon the German positions north of the Aisne. The struggle for and around Rheims. The operations on and against the German right flank. In this chapter it is proposed to deal with the attack upon the German positions north of the Aisne. The manner in which the British troops forced the passage of that river and secured a footing on the ridge, and held on to it, forms a particularly brilliant feat of arms. As stated in the official account:-- The country across which the army has had to force its way is undulating and covered with patches of thick wood. Within the area which faced the British before the advance commenced, right up to Laon, the chief feature of tactical importance is the fact that there are six rivers running right across the direction of advance, at all of which it was possible that the Germans might make a resistance. These are, in order from the south, the Marne, the Ourcq, the Vesle, the Aisne, the Lette, and the Oise. The Lette, it may here be stated, is a tributary of the Oise. Rising just to the north of Craonne and flowing westward through an upland valley, it is used in the lower part of its course as a section of the Oise and Aisne Canal.