It was comparatively late in the war before special bombing machines were evolved. They were then divided into day-bombers and night-bombers, the D.H.9 and 9a machines being typical of the former and the Handley Page of 1917--a large twin-engine aeroplane, the first really effective night-bomber, of considerable carrying power but low performance--of the latter. By November 8th, 1918, two super-Handley Pages were ready to start to Berlin. They possessed a maximum range of 1,100 miles, a crew of seven, four 350 horse-power Rolls-Royce engines, arranged in pairs, a tractor and a pusher in tandem on either side of the machine, and, as they would be compelled to fly both by night and day, a gun defence system. The D.H.10a and the Vickers Vimy, for day and night bombing respectively, were also being produced at the date of the Armistice. In the early days of the war an aeroplane had little to fear above 4,000 feet. With the improvement of the anti-aircraft gun there was, by the end of the war, no immunity at 20,000 feet. Very low flying for attack was, however, being rapidly developed, and would have proved of great effect in 1919. The aeroplane used for this purpose was the single-seater fighter, and the Sopwith "Salamander," with two guns, a speed of 125 miles an hour, and 650 lb. of armoured plates, was about to make its appearance at the Armistice. I have previously mentioned how dependent the improvement of design and performance of aircraft has been upon the less simple and tardier development of the engine. The invention of the light motor made aviation possible, and development has synchronized with the evolution of lighter, more powerful and more reliable engines. One of the most difficult problems still confronting us is the production of a cheap, high-powered and reliable engine, but the existence at the end of the war of machines weighing 15 tons indicates the progress achieved, while British engines of 600 horse-power are now in use, and one of 1,000 horse-power will shortly be available. TACTICS AND THE STRATEGIC AIR OFFENSIVE. During the war there were three concurrent movements in process: the ratios of the various forms of air tactics were constantly changing, and the components of our air forces varied in accordance with the development of reconnaissance, artillery co-operation, bombing and fighting. Secondly, their total strength was increasing rapidly; and, thirdly, it was increasing relatively faster than the Army or Navy.