THE TEXT-BOOKS.--Changes in tactical methods are recorded from time to time in circulars issued by the General Staff, to be embodied eventually in the official text-books. These text-books ("Infantry Training" and "Field Service Regulations") are the foundation upon which the study of Infantry Tactics should be based, and of these books Colonel G. F. R. Henderson has left behind him the following opinion: "That portion of our own text-books which refers to Infantry in Attack and Defence is merely the essence of Tactics. There is no single sentence that is not of primary importance, no single principle laid down that can be violated with impunity, no single instruction that should not be practised over and over again." After four years of warfare, in which the principles enunciated in the text-books had been put to the most searching of all tests (_i.e._ practical application in War), the General Staff of the Army was able to preface a list of its recent publications with the following exhortation: "It must be remembered that the principles laid down in Field Service Regulations and in Infantry Training are still the basis of all sound knowledge." At the close of the final victorious campaign, Marshal Haig emphasised the truth of this claim: "The longer the war lasted the more emphatically has it been realised that our original organisation and training were based on correct principles. The danger of altering them too much, to deal with some temporary phase, has been greater than the risk of adjusting them too little. . . . The experience gained in this war alone, without the study and practice of lessons learned from other campaigns, could not have sufficed to meet the ever-changing tactics which have characterised the fighting. There was required also the sound basis of military knowledge supplied by our Training Manuals and Staff Colleges." [1] Author of "Ben Hur." [2] For an example in military fiction, see _The Second Degree_ in "The Green Curve." [3] "Unus homo nobis cunctando restituit rem." [4] The term "field gun" was limited to the 18-pounder until the _Boer War_, when heavy guns were used as mobile artillery. In the Great War, mechanical transport brought into the field of battle guns of the largest calibre. Quick-firing field guns were first used by the Abyssinians against the Italians at the Battle of Adowa (February 29, 1896). [5] Reconnoitring balloons were first used by the Army of the Potomac at the Battle of Fredericksburg (December 12, 1862). Aeroplanes were used in warfare for the first time in 1911, during the Italo-Turkish campaign in Tripoli, North Africa. [6] Heavily armoured cars, known as "Tanks," were introduced during the First Battle of the Somme, September 15, 1916. {24} THE BATTLE "Theoretically, a well conducted battle is a decisive attack successfully carried out."--MARSHAL FOCH.