The opposing lines have buried themselves in mazes of entrenchment. On both sides old methods of warfare and weapons forsaken or forgotten for centuries have again been gradually resorted to. The “Minenwerfers,” the trench guns, are nothing but the old-fashioned mortar much improved upon. The jet of liquid fire driven by compressed air, finds its prototypes in the Greek fire of Constantinople and the hand-thrown combustibles--boiling oil and burning pitch--of the Middle Ages. STRATEGY. The rules of strategy remain immutable. They still consist in attacking the enemy on one of his wings; in attempting to outflank him on one side; in trying to cut his line in two by a blow in the centre; in organizing a system of transportation so that the necessary forces may be quickly assembled at the points which are to be attacked or protected; in taking advantage of a superiority due to the possession of well-organized interior lines. Such are the ancient basic principles, that, in various combinations, have been applied by contending armies since the dawn of military science. _Examples._ When the Germans attacked on the Yser front, their purpose was twofold: 1st. To outflank the left wing of the Franco-Anglo-Belgian Army; 2d. To force their way towards Calais and Dunkirk so as to prevent England from using those harbours for the concentration of her armies in France. After her failure on the Yser front, Germany made use of her superiority in interior lines, composed of the railway lines existing before the war, supplemented by new ones built as they were needed for military operations. Owing to her central geographical position, Germany is able at all times to dispatch forces from the heart of her Empire to the various fronts; from Russia to the French Front, and _vice versa_. To these interior lines is due the facility with which she has quickly concentrated large masses of troops at any desired point, notably on the Roumanian front at the end of 1916. When she had firmly consolidated her Western Front she rapidly collected all her available forces on the Eastern Front in an effort to crush the Russians. When, in February, 1916, the Germans launched the gigantic attack against Verdun, it was with a twofold strategic purpose: 1st. To pierce the French line between right wing and centre and resume the march on Paris. 2d. In case of a partial success, to strengthen themselves by the occupation of Verdun, with a view to preventing the French armies from reaching the right bank of the Meuse, while at the same time guarding their own left wing and their communications with Metz, should circumstances ever force them to withdraw behind the Meuse. During the autumn of 1915 the French attempted to avail themselves of the comparative weakness of the Germans due to their campaign against Russia. A favourable issue would have taken them to Vouziers-Rethel, and very possibly have caused all the German lines to be withdrawn from around Rheims and Soissons.