In these circumstances he therefore started with the odds considerably in his favour; and yet, as will be seen, as far as the Highland Division was concerned, he seldom met with the success he anticipated. His plan was to form up his consolidating party as close to the place where the crater was to be blown as was safe. He then blew the mine, and simultaneously opened a barrage of artillery, trench-mortars, and rifle grenades, &c., on the two flanks and on the British side of the crater. He thus hoped to deny to our troops access to it. Under cover of this barrage he then rushed his assaulting parties up to the crater, and attempted to consolidate posts both on the near and far lips. Immediately, therefore, that a mine was blown, parties had to be organised to rush to the crater and seize at least the near lip. These parties had, of course, no previous knowledge as to the time at which the mine was to be exploded. They were also liable to be temporarily disorganised in the general confusion caused by the explosion. Thus, as a rule, when the crater fighting began, the enemy was already on the near lip before our parties were fairly on the scene. A closely-contested fight would then ensue with bombs, Lewis guns, and rifles, and would continue until the enemy had been ejected at all events from the near lip. Posts would then be established on it, and a sap would be dug connecting the posts to the foremost British trench. In these encounters casualties were frequently heavy, as the parties had often to pass through a heavy barrage, followed by their bomb carriers. The latter were employed in large numbers, as in this form of warfare several hundred bombs were often thrown in one night. On first taking over, the mining situation was obscure. The French tunnellers had been withdrawn, leaving only old French Territorials to man the listening galleries. These veterans considered this duty _très dangereux_, as indeed it was. In consequence, the period was marked by a constant state of anxiety as to what portions of the line were safe from the possibility of being blown up at any moment. However, on the arrival of the British tunnelling companies, which were again largely reinforced by the coal miners in the Division, accurate information was soon obtained as regards the enemy's underground activity. The defensive galleries were first perfected, so that timely warning could be given of any mine that he was likely to explode. By this means camouflets could be used to hinder his progress. Subsequently it became possible to take the offensive, and mines were blown to destroy his crater positions and trenches. Later, when heavy calls were made upon the German troops to sustain the fighting on the Somme, they were compelled to relax their efforts in this sector, with the result that the British tunnellers established a marked superiority over them.