But if their co-operation with the cavalry was imperfect and disappointing, the work done by aeroplanes a few days later, during the army manoeuvres, was a complete vindication of the Flying Corps. There were two divisions on each side; the attacking force, under Sir Douglas Haig, advanced from the east; the defending force was commanded by General Grierson. The services rendered to the defence by the airship _Gamma_ have already been described. The fatal accidents of the summer and the consequent prohibition of monoplanes diminished the available force of aeroplanes, but a squadron of seven was allotted to each side. Major Burke's squadron, with its headquarters at Thetford, operated with the attacking force; Major Brooke-Popham was with the defence at Cambridge. Operations started at six o'clock on the morning of Monday, the 16th of September. At a conference on Sunday afternoon, General Briggs, who commanded the cavalry on the side of the defence, told General Grierson that the forces were far apart, and he could not hope to bring in any definite information till Tuesday. General Grierson was then reminded by his chief staff officer that he had some aeroplanes. 'Do you think the aeroplanes could do anything?' he asked of Major Brooke-Popham, and on hearing that they could, ordered them to get out, 'and if you see anything, let us know.' Monday morning was fine and clear; the aeroplanes started at six o'clock; soon after nine o'clock they supplied General Grierson with complete, accurate, and detailed information concerning the disposition of all the enemy troops. During the rest of the manoeuvres he based his plans on information from the air. On his left flank there were only two roads by which the enemy could advance; he left this flank entirely unguarded, keeping one aeroplane in continual observation above the two roads, and so was able to concentrate the whole of his forces at the decisive point. In the course of a few days the aeroplanes rose into such esteem that they were asked to verify information which had been brought in by the cavalry.