In all the dispositions which were made for a watch on the northern entrance to the North Sea, the principle kept in mind was the necessity for such an organisation of the patrols as to have, in so far as numbers permitted, two lines, or two areas, watched. The two areas were at such a distance apart that vessels moving in or out of the North Sea were forced, so far as all human foresight could provide, to pass through the waters occupied by one of the two groups of ships during daylight hours; the distances apart were regulated according to the length of the night at the different seasons of the year. As the Battle Fleet worked farther to the northward and westward, it became possible to make use of the heavy ships to assist in blockade work without running undue risks from submarines, and the blockade increased correspondingly in effectiveness. As time went on, however, the provision by the Admiralty of a larger number of armed merchant cruisers enabled us to establish an effective blockade line by the use of these vessels alone, backed up by Cruiser Squadrons when such were available. The withdrawal of the Battle Fleet to more northern and western waters first took effect when the Fleet Base was shifted temporarily from Scapa to Lough Swilly. When this occurred, it did not affect the policy of frequent cruiser sweeps into the southern portion of the North Sea, supported by the Battle Fleet, which were still continued. The dispositions that have been described took account naturally of two other very important factors. The first was the transport of our Expeditionary Force to France. It was highly probable that the enemy would endeavour to interfere with this movement, and in the early days of the War it would not have been a difficult matter for him to cause us some loss. His failure to make at least some attempt in this direction showed a lack of enterprise which surprised me, as I think it surprised most naval officers. The conditions for him were distinctly favourable. Our main Fleet was based, as he must have been aware, far away to the northward, and if he had timed an attack on the cross-Channel traffic for a period during which he reckoned that the Grand Fleet, or at least the destroyers, were returning to the base to fuel, he would have stood a good chance of making the attack and returning to his base before that Fleet could intervene. Consequently, he would only have had to deal with the comparatively light forces based in southern waters. On the other hand, if our Fleet arrived on the scene without destroyers, the Germans would have possessed no mean advantage.