Recognition marks on aeroplanes were at this time, and indeed throughout the war, a matter of great difficulty. It had been suggested before the war that they would not be necessary, but the reverse was found to be the case, as even with the distinctive marks which were adopted our machines were often fired at by British troops, and we should undoubtedly have lost very heavily if we had flown over our own lines with false marks, as was suggested, or none. _Bombing._ The bombing operations, which reached their climax in the raids on German industrial centres in 1918, arose from very primitive methods used at the beginning of the war. During the retreat from Mons a few hand grenades were carried experimentally in the pockets of pilots and observers, or, in the case of the larger varieties, tied to their bodies, and these were dropped over the side of the machine as opportunity occurred. At the Marne, for instance, small petrol bombs set fire to a transport park and scattered a mixed column of infantry and transport. I think I am right in saying that the first German bombs were dropped on us--unsuccessfully--at Compiegne on August 29th, 1914. It was not, however, until the beginning of 1915 that special bombing raids were started by the Royal Flying Corps, one of the first places to be attacked being the Ghistelles aerodrome in West Flanders. The most important bombing operations and raids into Germany in the early days of the war were carried out by the Naval Air Service, units of which landed at Ostend on August 27th and operated with the Royal Naval Division from Antwerp. They were subsequently withdrawn to Dunkirk to form the nucleus of an aircraft centre from which excellent work was done in attacking the bases established on or near the Belgian coast from which German submarines and airships conducted their operations. Just before the Germans entered Antwerp, the first raid was made against a German town, one machine reaching Dusseldorf, when it descended from 6,000 to 400 feet and dropped three bombs on an airship shed. From the end of 1914 onwards the activities of the Royal Naval Air Service in this theatre of operations continually increased, the chief objectives being the gun emplacements at Middelkerke and Blankenburghe, the submarine bases at Zeebrugge and Bruges, the minefield and dock of Ostend, the airship sheds near Brussels, and the dockyards at Antwerp. The first airship destroyed in the air was attacked over Ghent. An interesting experiment was the attempt by the R.N.A.S. at the Dardanelles to sink the heavy wire anti-submarine net, which had been stretched on buoys across the Straits at Nagara by the Turks, by means of parachute bombs.