The overseas work of the Naval Air Service during the closing months of 1914, from the battle of Ypres onwards, can be briefly stated. It consisted of help given to the British army, reconnaissances and attacks carried out along the occupied coast of Belgium, and two great air-raids.

During the battle of Ypres one naval aeroplane was working for the First Army Corps. Reconnaissances were carried out daily by the few available machines. Squadron Commander Davies on three occasions attacked German machines in the air; they escaped by planing down to behind their own lines. Flight Lieutenant Collet, whose aeroplane had been wrecked, flew as observer to Squadron Commander Davies, and reported the positions of six new German batteries. Flight Lieutenant Pierse, in an old inefficient machine which climbed badly, made many flights along the coast, and was wounded by shrapnel in the air over Antwerp.

Meantime, on the 31st of October, a seaplane base was established at Dunkirk in the works of the shipbuilding company, which occupied a part of the harbour. Under Squadron Commander J. W. Seddon the seaplanes did some good work; they located enemy guns, dropped heavy bombs on Bruges railway station, co-operated with the ships' guns in the bombardment of the coast, kept a look-out for German submarines, and reported on the enemy defences.

This base at Dunkirk remained an active centre for our seaplane and aeroplane work throughout the war, and did much to defeat the German plans. The possession of the coast of Flanders had a twofold value for the Germans; it served to safeguard the right flank of their invading army and it provided them with a base both for their submarine campaign and for occasional attacks on the naval forces which held the Dover Straits. There can be no doubt that it was part of their plan to take permanent possession of the Belgian coast. It is not easy to understand why, before the war, when Zeebrugge and Ostend were made into fortified harbours, a clause was inserted in the contractors' orders that the mole at Zeebrugge should be fit to carry hundred-ton guns and to withstand heavy gun recoil; also, that the Zeebrugge and Ostend locks and basins should be capable of accommodating a flotilla of torpedo-boats. These things were not done in the interests of England, nor had the Belgian Government any reason to fear naval aggression from the west. The plans which had this beginning were developed and completed during the first two years of the German occupation. Bruges, which was joined by canals both to Zeebrugge and Ostend, became the naval headquarters of the German forces, the base for submarines and torpedo-craft, and the centre for construction and repair. Everything was organized on a solid basis, as if to endure; yet at some time during the third year of the war the enemy must have begun to feel doubtful whether he could keep his hold on the Belgian coast. About thirty miles along the coast from Ostend, and forty or more miles from Zeebrugge, lay the port of Dunkirk, occupied in strength by the navies of France and Great Britain, and by the Royal Naval Air Service. Dunkirk was a thorn in the side of the Germans. The docks and harbours at Bruges, Zeebrugge, and Ostend were incessantly bombed from the air. Ships and works were seriously damaged, but the effect on the morale of the German forces was even more considerable. Repeated alarms, which sent all hands to take shelter in dug-outs, interfered with the work of every day. In the main basin at Bruges, and alongside the Zeebrugge mole, shelters, jutting out over the water, were provided for submarines and destroyers. The respect felt by the Germans for the menace of Dunkirk is perhaps best witnessed by the fierce nightly attacks from the air which they made on the town during the later period of the war. Admiral Sir Reginald Bacon, who commanded the Dover Patrol from April 1915 Until the end of 1917, speaks of these as 'the martyrdom of Dunkirk'. A great many of the houses in the town were levelled with the ground. Yet the inhabitants, knowing that they were maintaining a force which gave as good as it got, went about their daily business cheerful and unperturbed. They were rewarded in the end. When, after the armistice, the last German submarine came through the lock-gates at Zeebrugge, with her crew fallen in on the fore superstructure, her captain called for three cheers,—'As that's the last you'll see of Flanders.' The cheers were given very heartily—an involuntary tribute to the four years' work of the naval services at Dunkirk.

All these things were yet to come when the third of the naval aeroplane raids into enemy territory was made on the 21st of November 1914. This, the successful attack on the Zeppelin sheds at Friedrichshafen, Lake Constance, was planned and executed to perfection. Lieutenant Pemberton Billing, of the Royal Naval Volunteer Reserve, left England on the 21st of October under Admiralty instructions. He arrived at Belfort on the 24th and, by the courtesy of the French general in command, obtained permission to use the aerodrome within the fortifications and its large dirigible shed as the starting-point for a raid. German spies were believed to be at work in Belfort, so arrangements were made for the machines to be brought into the place by road transport at night, and for their pilots to be boarded and lodged, during the whole of their stay, in the dirigible shed. Having completed these preliminaries, Lieutenant Billing carried out discreet inquiries which enabled him to draw up a chart of the proposed route, a complete plan of the Zeppelin factory, and a draft of instructions for the proposed raid.

Meantime the French had themselves been meditating a raid on Friedrichshafen, and the Governor of Belfort had received some valuable reports on the factory and the prevailing weather conditions. After some discussion it was decided that as Zeppelins were intended to assist in the destruction of the British fleet, the Royal Naval Air Service should be privileged to pay the first visit, but that this privilege should lapse if the visit were not paid within thirty days.

In the season of late autumn, when the barometer is high and the air calm, the whole of the Swiss plateau and the Rhine valley bordering it is often plunged in a thick mist which reaches to a height of about 3,000 feet. Above this sea of mist the air is clear and the flight of an aeroplane safe and easy. The course chosen from Belfort to Lake Constance, a distance of about 125 miles, was bent, like an elbow at an obtuse angle, round the northern border of Switzerland, so that Swiss neutrality should not be violated. It lay over country much of which is wooded and sparsely inhabited—first from Belfort to Mülhausen, thence over the Black Forest and some groups of wooded peaks to a point north of Schaffhausen. Here the prescribed course was to bend southwards, between the two arms of Lake Constance which stretch to the north-west, and when once the lake was reached the objective would be full in view.

On the 28th of October Lieutenant Pemberton Billing returned to England to collect men and machines. A squadron of four Avros, with 80 horse-power Gnome engines, had already been formed at Manchester under Squadron Commander P. Shepherd. The four pilots were: