The progress made enabled us first to hold our own against the German artillery, then to equal it, and finally to surpass it. Considering the limited means left to France by the invasion, considering the seizure by the enemy of her Lorraine iron deposits, and of her richest coal mines, it must be acknowledged that the effort made from 1915 to 1917 was gigantic. =2. Different sorts of artillery.= We shall divide the artillery into three parts: the artillery of an army, of an army corps, and of a division. ARTILLERY OF AN ARMY. This includes heavy artillery of all sizes. The army unit alone possesses guns of greater calibre than 155 mm. The composition of the heavy artillery in an army varies considerably, the number of different types of cannon allotted to any one arm depending upon circumstances and on the work which it is expected to do. According to local needs, therefore, the Generalissimo orders the heavy artillery to be transferred from one army group to another. Similarly, the Chief of a group of armies can, as he sees fit, order such transfers of guns within his command. We find in the armies howitzers and mortars of the following sizes: 220, 270, 280, 305, 370, 400 mm. (in inches: 8, 10, 11, 12, 14½, and 15¾). Soon we shall have 520 mm. guns (20½ inches). There are also field guns of 120 and 155 mm. short and 155 mm. long (5 and 6 inches) and naval guns of 19, 100, 240, 274, 305, and 340 mm. The artillery of an army is under the command of a General. The field batteries of 120–155 mm. are composed of four pieces; howitzer batteries and naval batteries of 100 and 190 mm. are nearly always of two pieces. The largest mortars, and the heaviest naval guns mounted on railroad trucks, operate singly, and each gun is accompanied by several trucks carrying its material and munitions. ARTILLERY OF AN ARMY CORPS. The artillery of an army corps is under the command of a Colonel. It includes two groups of 75 mm. field guns, two groups of 105 (4 inch), or of 120 (5 inch), and one group of 155 (6 inch), quick-firing. This artillery is reinforced, in case of need, by the heavy artillery which the army can dispose of. The Colonel commanding the artillery assumes the command of all batteries, of whatever size, momentarily put at the disposal of his army corps. He is most specially intrusted with the selection of the ground on which to place the batteries, and it is he who has to specify the part each of them shall take in the action. The divisional batteries of the army corps are also under his command, at least during the preparation for the attacks. It is absolutely indispensable that each battery should be assigned its objective, and should be positively forbidden to scatter its projectiles promiscuously. Thus costly waste is avoided, and a definite purpose accomplished.