In 1916 and the early part of 1917 we were but ill provided with aircraft suitable for anti-submarine operations at any considerable distance from the coast, and such aircraft as we possessed did not carry sufficiently powerful bombs to be very effective in attacking submarines, although they were of use in forcing these vessels to submerge and occasionally in bringing our surface craft to the spot to press home the attack. The Royal Naval Air Service, under Commodore Godfrey Paine, devoted much energy to the provision of suitable aircraft, and the anti-submarine side of the Naval Staff co-operated in the matter of their organization; with the advent of the large "America" type of seaplane and the Handley-Page type of aeroplane, both of which carried heavy bombs, successful attacks on enemy submarines became more frequent. They were assisted by the airships, particularly those of the larger type. Improvements which were effected in signalling arrangements between ships and aircraft were instrumental in adding greatly to their efficiency, and by the early summer of 1917 aircraft had commenced to play an important part in the war against submarines and in the protection of trade. Thereafter progress became rapid, as the following figures show: In June, 1917, aeroplanes and seaplanes patrolling for anti-submarine operations covered 75,000 miles, sighted 17 submarines, and were able to attack 7 of them. In September, 1917, the distance covered by anti-submarine patrols of aeroplanes and seaplanes was 91,000 miles, 25 submarines were sighted, of which 18 were attacked. In the four weeks ending December 8, 1917, in spite of the much shorter days and the far less favourable flying weather experienced, the mileage covered was again 91,000 miles; 17 submarines were sighted, of which 11 were attacked during this period. As regards airships the figures again show the increased anti-submarine work carried out: In June, 1917, airships engaged in anti-submarine patrol covered 53,000 miles, sighted and attacked 1 submarine. In September, 1917, they covered 83,000 miles, and sighted 8 submarines, of which 5 were attacked. In the four weeks ending December 8, 1917, they covered 50,000 miles, sighted 6 submarines, and attacked 5 of them. The airships were more affected by short days, and particularly by bad weather, than the heavier than air craft, and the fact that they covered practically the same mileage in the winter days of December as in the summer days of June shows clearly the development that took place in the interval. During the whole of 1917 it was estimated that our heavier than air craft sighted 135 submarines and attacked 85 of them, and our lighter than air craft sighted 26 and attacked 15. The figures given in Chapter IX of the number of submarines sunk during the war by aircraft (viz. 7 as a minimum), when compared with the number of attacks during 1917 alone suggest the difficulties of successful attack.