Orders were also given to discourage the usual stream of officers who ordinarily visited our front trenches prior to an operation, and who often, thoughtlessly, made a great display of unusual activity, under the very noses of the enemy front line observers, by the flourishing of maps and field-glasses, and by bobbing up above our parapets to catch fleeting glimpses of the country to be fought over. Such reconnaissance, however desirable, was to be confined to a few senior Commanders and Staff Officers. All subordinates were to rely upon the very large number of admirable photographs, taken regularly from the air, both vertically and obliquely, by the indefatigable Corps Air Squadron. These served excellently as a substitute for visual observation from the ground.

The prohibition against the movement of any transport in the daylight naturally very seriously hampered the freedom of action of the troops of all arms and services, but was felt in quite a special degree by the whole of the Artillery. Over 600 guns of all natures had to be dragged to and emplaced in their battle positions, and there camouflaged, each gun involving the concurrent movement of a number of associated vehicles. A full supply of ammunition had to be collected from railhead, distributed by mechanical transport to great main dumps, and thence taken by horsed vehicles for distribution to the numerous actual gun-pits.

As the amount of ammunition to be held in readiness for the opening of the battle averaged 500 rounds per gun, it became necessary to handle a total of about 300,000 rounds of shells and a similar number of cartridges of all calibres, from 3½ to 12 inches, not to mention fuses and primers, or the immense bulk and weight of infantry and machine-gun ammunition, bombs, flares, rockets, and the like, for the supply of all of which the artillery was equally responsible.[13] The great amount of movement involved in the handling and dumping of all these munitions, and the deterrent difficulties of carrying out all such work only during the short hours of darkness, must be left to the imagination.

The artillery was, however, confronted, for the first time, with a difficulty of quite a different nature. In the previous years of the war every gun, after being placed in its fighting pit or position, had to be carefully "registered," by firing a series of rounds at previously identified reference points, and noting the errors in line or range due to the instrumental error of the gun, which error varied with the gradual wearing-out of the gun barrel. By these means, battery commanders were enabled to compute the necessary corrections to be applied to any given gun, at any one time or place, so as to ensure that the gun would fire true to the task set.

Such registration naturally involved, for a large number of guns, a very considerable volume of Artillery fire, the extent of which would speedily disclose to the enemy the presence of a largely increased mass of Artillery, and would inevitably lead him to the conclusion that some mischief was afoot. Fortunately, however, the rapid evolution during the war of scientific methods had by this juncture placed at my disposal a means of ascertaining the instrumental error of the guns on a testing ground located many miles behind the battle zone. This method was known as "calibration," and consisted of the firing of the gun through a series of wired screens, placed successively at known distances from the muzzle of the gun. The whole elements of the flight of the projectile could then be accurately determined by recording the intervals of time between its passage through the respective screens. From these data could be deduced the muzzle velocity, the jump, the droop and the lateral error of each gun.

Simple and obvious as was the principle of such an experiment, the merit of the new process of calibration lay in the remarkable rapidity and accuracy with which the electric and photographic mechanism employed made the necessary delicate time observations, correct to small fractions of a second, and automatically deduced the mathematical results required. The calibration hut, in which this mechanism was housed, became one of the show spots to which visitors to the Corps area were taken to be overawed by the scientific methods of our gunners.

In the early days of August the calibration range of the Australian Corps was a scene of feverish activity. All day long, battery after battery of guns could be seen route-marching to the testing ground, going through the performance of firing six rounds per gun, and then route-marching back again the same night to its allotted battle position. So rapid was the procedure that long before he had reached his destination the Battery Commander had received the full error sheet of every one of his guns, and by means of it was enabled to go into action whenever required without any previous registration whatever. This great advance in the art of gunnery contributed in the most direct manner to the result that when these 600 guns opened their tornado of fire upon the enemy at daybreak on August 8th, the very presence in this area of most of them remained totally unsuspected.

The manner of the employment of the ponderous mass of Heavy Artillery at my disposal will be referred to later. The action of that portion of the Field Artillery which was to become mobile in the concluding phases of the battle has already been dealt with. It remains only to describe, in outline, the arrangements made for the normal barrage fire of the Field Artillery during the first phase.

It has been my invariable practice to reduce the barrage plan to the simplest possible elements, avoiding in every direction the over-elaboration so frequently encountered. By following these principles not only is the actual preparatory work of the Artillery greatly reduced in bulk and simplified in quality, but also the liability to mistake and to erratic shooting of individual batteries or guns, and consequent risks of damage to our own Infantry, are greatly diminished. These advantages are bought at the small price of calling upon the Infantry to undertake, before the battle, such rectifications and adjustments of our front line as would accommodate themselves to a straight and simple barrage line. This is in sharp contrast to the much more usual procedure which prevailed (and persisted in other Corps to the end of the war) of complicating the barrage enormously in an attempt to make it conform to the tortuous configuration of our Infantry front line.