As with hand-grenade fighting, mine-warfare too suffered a kind of resurrection in entrenched warfare. In the siege of Port Arthur it had already once again played an important part. It was only natural that from the moment that the operations took on the nature of a siege all the available weapons should be brought into play, both those which had been utilised previously and improved by the aid of modern technical science, and also those of recent invention. Thus, for warfare at close quarters, flame-throwers, bomb-throwers, the trench-mortars of earlier days in an improved form, trench cannon and muskets came into use, while the machine-guns acquired a growing importance, corresponding with their great increase in numbers. With the introduction of appliances for blowing gas from reservoirs and of gas-grenades, entirely new weapons of war made their appearance. And these in their turn called for special means of defence in the shape of gas-masks. The English and the French sought to prepare the way for their attacking troops by the employment of battle-motors--the so-called tanks. Altogether, this War, as a result of the development of modern technical science, has led to inventions and improvements such as no previous war has ever witnessed. It will always redound to the special glory of German industry, and above all of Germany's chemical industry, that in this sphere it engaged in and carried through a struggle against the industry of the whole world. The supplies of artillery ammunition which had been provided for the War proved in the case of all the belligerent States to be very far below the requirements. Especially in the late autumn of 1914, our troops found themselves more than once in a critical situation as a result of this shortage. None the less, it was impossible that such immense supplies as were actually required should have been stored up in peace time. Our industry, however, succeeded in satisfying to an ever-increasing extent the demands which had to be made upon it; it was able, by its unaided effort, to keep pace with the enormous supplies which poured in to our enemies from America and (in the case of Russia) from Japan. As a result of the manner in which the positions were more and more adapted to the ground or artificially concealed, high-angle-firing artillery gained in importance. At the beginning we possessed in our numerous mobile heavy high-angle-fire batteries a certain superiority over the French, which, however, they were able in part to make up for by the extremely skilful use and appropriate grouped disposition of their artillery. Later on in the War, the French and the English brought into action guns of very heavy calibre, which hurled immense quantities of shells against our trenches.