Four squadrons of the Military Wing, or Royal Flying Corps, that is to say, forty-eight machines, with a few additional machines in reserve, bore a part in the retreat from Mons. A detachment of the Naval Wing, or Royal Naval Air Service, was sent to Belgium, and after bearing a part in the defence of Antwerp, established itself at Dunkirk, which remained throughout the war a centre for aerial operations. These were the beginnings; in the four years and three months of the war the air service grew and multiplied a hundredfold. At the date of the armistice, the 11th of November 1918, there were operating in France and Belgium ninety-nine squadrons of the Royal Air Force. In August 1914 there had been less than two hundred and fifty officers in the service, all told; in November 1918 there were over thirty thousand. In August 1914 the total of machines, available for immediate war service, was about a hundred and fifty; in November 1918 there were more than twenty-two thousand in use, almost all of them enormously more powerful and efficient than the best machines of the earlier date. In the course of the war our air forces accounted for more than eight thousand enemy machines; dropped more than eight thousand tons of bombs on enemy objectives; fired more than twelve million rounds of ammunition at targets on the ground; took more than half a million photographs; brought down nearly three hundred enemy balloons; and suffered a total of casualties not far short of eighteen thousand. Not less important in its influence on the fortunes of the war than any of these achievements, perhaps more important than all of them, was the work done by aircraft in detecting movements of the enemy and in directing the fire of our gunners upon hostile batteries. This work cannot be exactly assessed or tabulated, but the German gunner knew where to look for the enemy he most dreaded. A rapid summary of this kind shows that the history of the war in the air is inseparable from the history of the development of the art of flying. Of those who were competent to handle a machine in the air during the years before the war by far the greater number served with the colours. With the outbreak of war civilian flying, except for training purposes, abruptly ceased. The necessities of war compelled and quickened invention. When a nation is fighting for its life, money and energy are expended without check, and it may be doubted whether in the whole history of mankind any art in its infant stage has been so magnificently supported and advanced by war as the art of flying was supported and advanced by the greatest war of all.