Situated in Schleswig, not far from the Danish border, its ships were available equally for reconnaissance in the North Sea or the Baltic, including the Kattegat, and all the devious straits and passages between Denmark and the Scandinavian Peninsula. In a way, with the seaplane station at Sylt, it formed the first line of defence against the ever increasing British mine-laying sorties in the North Sea and Kattegat. The actual attacks against these mine-layers came to be left more and more to the seaplanes, though, in the first years of the war, considerable bomb-dropping was attempted here from Zeppelins. The vulnerability of the airship to aeroplane attack--and, notably, the destruction of a Zeppelin by a plane launched from the light cruiser _Yarmouth_--put an end to their work in this _rôle_, and compelled them to confine their activities entirely to reconnaissance. It was the great effectiveness of the long observation flights from Tondern which determined the R.N.A.S. to make a strong endeavour to put an end to the menace by destroying the sheds. Besides greatly hampering the British mine-laying program they were also credited with supplying the Germans with invaluable information for both their surface raids and submarine attacks on the Norwegian convoys. The only way in which Tondern could be reached was by machines launched from a carrier ship, and for this purpose the _Furious_, on account of her great speed and size, was perhaps better adapted than even a ship of the type of the _Argus_, in spite of the fact that the latter was specially built for the work, while the former was converted from a cruiser of the _Courageous_ class. The raid, as any attempt of the kind must be, was prepared for some time in advance, and was only launched when it appeared that all conditions were especially favourable for its success. Probably the astonishing Admiralty intelligence service played an important, perhaps a decisive, part.