When at the end of October the Belgian army mortgaged great tracts of their ground for many years by opening the canal sluices and letting in the sea, the Germans were enabled to divert the Third Reserve Corps southwards. The movements of troops from this area were observed by the Royal Flying Corps, and General Headquarters on the 1st of November issued this summary: 'The coast road from Ostend to Nieuport was reported clear this morning, and there are indications generally of a transference of troops from the north of Dixmude southwards.' Again, when the attack on Ypres had failed and died away, the Germans transferred many troops from the western to the eastern front; these movements also were seen by the Royal Flying Corps, who reported on the 20th of November an abnormal amount of rolling stock at various stations behind the German front. 'The rolling stock formerly parked on the Ostend-Thourout and Ostend-Roulers lines has evidently been broken up', says General Headquarters Intelligence Summary for the 20th of November, 'and distributed to a number of stations along the Lys and in the area immediately north of it, which would be suitable points of entrainment for the forces in that district.... This redistribution of the rolling stock, together with the apparent reduction in motor transport, would seem to point to some important movement away from this immediate theatre being in contemplation.' Air reports for the following day proved that much movement eastwards had already taken place. Throughout the battle tactical reconnaissances had been maintained to a depth of from fifteen to twenty miles behind the German lines. There were some few fights in the air, and a little bombing, but observation was still the principal duty of the Royal Flying Corps. They were greatly privileged; at a time when our people at home knew nothing of what the army was doing, they, and they alone, witnessed the battle of Ypres. They would gladly have done more. Many of them had been infantry officers, and were eager to lend a hand to the infantry in that heroic struggle, but they lacked the means. Not until the summer of 1916 were they able, by organized attacks from the air, to help to determine the fortunes of a battle. With the close of the battle there came a lull in the fighting. This lull continued throughout the dark and damp of the first winter, and the interest of the war in the air shifts to the preparations which were being pressed forward at home for renewing the war during 1915 on a larger scale and with better material.