Practice has refuted this theory. The British aerial raids upon Cuxhaven and other places would have been impossible, and probably valueless as an effective move, but for the fact that it was possible to release the machines from a certain point upon the open sea, within easy reach of the cooperating naval squadron. True, the latter was exposed to hostile attack from submarines, but as results proved this was easy to repel. The aircraft were enabled to return to their base, as represented by the rendezvous, to be picked up, and to communicate the intelligence gained from their flight to the authorities in a shorter period of time than would have been possible under any other circumstances, while the risk to the airmen was proportionately reduced. The fact that the belligerents have built up such huge aerial navies conclusively proves that the military value of the Fourth Arm has been fully appreciated. From the results so far achieved there is every indication that activity in this direction will be increased rather than diminished.