The enemy thus possessed all the advantages of close observation over our lines; while, in addition, from the upper slopes of the Ridge, he obtained a magnificent panoramic view of the whole of the areas in rear of the British trench systems. On a clear day he could see from Thelus as far westwards as the road running from Habarcq to the Hermaville-Arras road. Moreover, south of the Scarpe, Observatory Ridge stared down at Roclincourt and Ecurie. The French, to neutralise his facilities for observation, had constructed communication trenches of what seemed interminable length. These ran from Anzin, Marœuil, and Mont St Eloi to the fire trenches, none of these villages being within two miles of the front line. The labour of walking along these trenches, all cut on a very winding pattern, was severe. It, however, fortunately transpired that the French in constructing trenches of this length had either flattered the enemy's vigilance, or that his vigilance had subsequently diminished, as it proved unnecessary to walk inside the trenches, certainly for the first three-quarters of a mile. The enemy did, however, keep a sharp look-out for movement on the roads within range of his artillery. He had, shortly before the Division arrived, killed a French regimental commander who took the liberty of riding on horse-back along the Arras-Bethune road. These long communication trenches were admirably dug by the French Territorials, who had constructed them, and were still standing and in daily use when the Division returned to this sector in February of the following year. In the British lines the defended village of Ecurie, about 100 metres above sea-level, afforded a good view of Thelus and of the enemy's defences at a distance of from 400 to 500 yards behind his front line. Observation of his front-line trenches could in most places only be obtained from observation posts in the forward area. The relief of the French 23rd and 24th Divisions of the XII^{me} Corps d'Armée was completed by 14th March. It was carried out during a blizzard of great severity, which continued for forty-eight hours. During this period the troops could do no more than remain where they had been placed by their guides, or misplaced as the case might be. During the relief and, in fact, until the blizzard abated, officers and men had only a hazy idea as to where they actually were. Similarly commanders were ignorant of the position of their troops. All three infantry brigades were in the line--the 154th Brigade on the right in the vicinity of Roclincourt, the 152nd in the centre, and the 153rd on the left. When the weather cleared, it was found that the Division had taken over from the French an unintelligible tangle of trenches dug in what can only be described as a vast cemetery, in which the earth in many places barely covered the dead.