Serious difficulties affecting the mobility of aircraft were the means of providing a regular supply of fuel and the selection of landing grounds when moving camp, which had to be close enough behind the front line as not to entail waste of time in flying out and back over friendly territory. This was later brought home to us in a very acute form during the Retreat from Mons. As machines improved, increasing attention was paid to bettering their power of reconnaissance by air photography, their value in co-operation with artillery by wireless equipment, their offensive action by bomb dropping and their offence and defence by armament. The value of a correct initiative and the aeroplane's role as an offensive weapon were fully appreciated and brought out in the Training Manual of the Royal Flying Corps which we compiled at Farnborough, and which was published early in 1914 by the War Office. It says:-- "It is probable that one phase of the struggle for the command of the air will resolve itself into a series of combats between individual aeroplanes, or pairs of aeroplanes. If the pilots of one side can succeed in obtaining victory in a succession of such combats, they will establish a moral ascendancy over the surviving pilots of the enemy, and be left free to carry out their duties of reconnaissance. The actual tactics must depend on the types of the aeroplanes engaged, the object of the pilot being to obtain for his passenger the free use of his own weapon while denying to the enemy the use of his. To disable the pilot of the opposing aeroplane will be the first object. In the case of fast reconnaissance aeroplanes it will often be advisable to avoid fighting, in order to carry out a mission or to deliver information; but it must be borne in mind that this will be sometimes impossible, and that, as in every other class of fighting, a fixed determination to attack and win will be the surest road to victory." Speaking generally, the evolution of the machine, as apart from the engine, which hung behind, followed upon the evolution of air tactics. As soon as experience, often hard won at the cost of a valuable life, opened up new fields of activity for aircraft, the designer and constructor evolved new designs to meet the new requirements. It was no small achievement in this period to have solved the problem of inherent stability, both in theory and practice, so successfully, that from the aerodynamic standpoint our machines in 1914 compare favourably with those in use at the end of the war.