It was not until October, 1917, that the first striking force, consisting of three squadrons, was formed under the Army with Ochey as its base. It was mainly used in raids against the ironworks in the Alsace-Lorraine Basin and the chemical industry in the neighbourhood of Mannheim. As I have said, a definite offensive policy by means of an independent strategic force was later decided upon, and the "Independent" Air Force was brought into existence. It originally comprised two day-bomber and two night-bomber squadrons. During the summer additional squadrons were allotted to it, including D.H.9's and Handley Pages. Day-bombing squadrons had to fight their way to objectives in close formation, and the problems connected with navigation, calculation of petrol supply, action of wind and ceiling, were all accentuated. Casualties were heavy, with the result that a squadron of Fighters, composed of Sopwith "Camels," was incorporated for the purpose of protection. Thus we see the beginnings of an air fleet analogous to the naval fleet with its capital ships and protective craft. The main objectives were the centre of the chemical industry at Mannheim and Frankfort; the iron and steel works at Briey and Longwy and the Saar Basin; the machine shops in the Westphalian district and the magneto works at Stuttgart; the submarine bases at Wilhelmshaven, Bremerhaven, Cuxhaven, and Hamburg, and the accumulator factories at Hagen and Berlin. It will be seen from a map that three of the main industrial centres were situated near the west frontier of Germany; and, therefore, one portion of the striking force was based at Ochey, which lies within a few miles of the Saar Basin, within 180 miles of Essen, and within 150 miles of Frankfurt. Another portion was based on Norfolk, where a group of super-Handley Page machines were established for the specific purpose of attacking Berlin, a distance of 540 miles, and the naval bases within 400 miles. It was obvious that though aircraft from England would have to cover greater distances, they would not expose themselves to the strong hostile defences in rear of the battle front. Three instances of the Independent Air Force's action may be cited. On the night of August 21st/22nd, two Handley Page machines dropped over one ton of bombs on Cologne Station, the raid occupying seven hours. On the night of August 25th/26th two Handley Pages attacked the Badische Aniline und Soda Fabrik of Mannheim; bombs were dropped from a height of 200 feet, direct hits being obtained in every case; and the machines then remained over the town, which they swept with machine-gun fire. On August 12th the first attack was made on Frankfurt by twelve D.H.4 day-bombers, every machine reaching the objective and returning safely in spite of being attacked, over Mannheim and throughout the return journey, by some forty hostile fighters.