This withdrawal considerably reduced the potentialities of this phase of the spring offensive. Instead of attacking from the Ancre northwards, simultaneously with the advance of the Third Army from the north-west, the Fifth Army had now to follow up the retiring enemy, and to dig itself in in front of the Hindenburg Line to which the enemy had withdrawn. The Hindenburg Line system, which subsequently became well known to the Highland Division, had been very strongly fortified and sited with great care and skill, so as to deny all advantages of position to any force attacking it. The enemy had thus already escaped from the great salient which it was hoped to nip off during the forthcoming operations. He was now established in the south of Arras in a position considerably stronger than that which he had vacated. As regards the sector held by the Division, the only other noteworthy incidents during the period of preparation for the attack were a succession of raids. These raids were carried out for two purposes: to obtain information concerning the enemy's garrison and defences, and to inflict the maximum amount of damage to his defences in view of the coming operations. The battle of Beaumont Hamel had disclosed how strongly the German could fortify himself in a chalk soil. The trenches which the Division was to attack, supported as they were by the commanding ground of the Vimy Ridge, comprised a most formidable defensive system. It was therefore arranged that raids should be carried out on a large scale on both brigade fronts, so that serious damage could be done to the entanglements and dug-outs, prior to the launching of the offensive. The first took place on 5th March, the raiding party consisting of 11 officers and 303 other ranks of the 6th Gordon Highlanders. The plan was to assault and capture the German front and support line on a frontage of 485 yards, and to remain in occupation of them for a period sufficient to allow time for the destruction of both the garrison and the dug-outs. Nine gaps were cut in the German wire on the frontage of attack by the artillery and the 2-inch mortars, the latter firing 1137 rounds during the process. Gaps were also cut, as a feint, along the whole Divisional front. The raid therefore ensured that a considerable amount of damage would be done to the enemy's defences prior to the big attack.