The ideas held in pre-War days as to the capabilities of submarines were found, after a short experience of war, to need modification. In the first place, it became quickly apparent that the German submarines possessed a radius of action and sea-keeping qualities considerably greater than those of our own submarines. It had been, for instance, looked upon as a considerable achievement for our submarines to keep the sea for a period of five to seven days, and they had not operated at any great distance from the coast. It is true that submarines had on occasion made long voyages such as to Australia, but they were then usually escorted, or even towed, and the number of days from port to port did not approach the length of time for which German submarines remained at sea. Further, it was known that the Germans possessed a considerable superiority in the number of submarines which were capable of operating overseas, and the frequent sighting of enemy submarines as far north as the Orkney and Shetland Islands early in the War, combined with the fact that it appeared that the enemy had established a regular submarine patrol in the centre of the North Sea, made it evident that the German submarines would constitute a very serious menace to our heavy ships. The comparative strength in submarines in Home Waters at the outbreak of war was as follows: _German_-- U Boats 28 of which U 1 to U 4 were hardly fit for oversea work, but were as good as our D class. _British_-- { of which D 1 was unreliable and the remaining D Class 8 { units of the D class were not equal to the { U boats. E Class 9 C Class 34 } Unfit for oversea work and used only for local B Class 3 } defence of the coast or in the Channel. The Germans also had at least 24 submarines under construction, whilst we were building 19, apart from two experimental vessels of which nothing resulted. Of these 19 submarines, several were of new type, in pursuance of a policy introduced by the Admiralty in 1913–14 of widening the area of supply of these vessels. This policy had far-reaching and beneficial results on the subsequent output of this class of vessel, as it enabled us to increase our submarine flotillas more rapidly than would otherwise have been the case.