The method employed was that of a sudden, violent shock, preceded by a short artillery preparation, mostly with smoke and gas shells, the aim of which was to put the men out of action, rather than to crush the defences. To this end, huge concentrations of troops were effected, in such wise that the masses of men could be thrown quickly and secretly at the presumed weak part of the Allies' front. The semi-circular disposition of the front facilitated the enemy's task, as the German reserves, grouped in the Hirson-Mézières region, in the centre of the semi-circle, could be used with the same rapidity against any part of the front-line from Flanders to Champagne. The point chosen by Ludendorff was the junction of the Franco-British Armies. To separate these two groups, by driving back the British, on the right, and the French, on the left; to exploit the initial success in the direction of the sea, isolating the British and forcing them back upon their naval bases of Calais and Dunkirk; then, having crushed the British, to concentrate the whole of his efforts against the French, who, unsupported and demoralized, would soon be driven to their knees,--such was apparently the strategical conception of the enemy's "Kaiserschlacht" or "Emperor's Battle". The Opposing Forces. On March 21, three German armies attacked along a 54-mile front, from the Scarpe to the Oise. In the north, the XVIIth Army (von Below) and the IInd Army (von Marwitz) attacked on either side of the Cambrai salient, but the main effort was made by the XVIIIth Army (von Hutier), which stretched from the north of St. Quentin to the Oise. [Illustration] Facing these armies were: the right of the British 3rd Army (Byng), extending from the Scarpe to Gouzeaucourt, and the British 5th. Army (Gough), from Gouzeaucourt to south of the Oise. The British expected the brunt of the attack to fall between the river Sensée and the Bapaume-Cambrai road, i.e. on the right of Byng's Army, which was reinforced accordingly, whilst the sector in front of the Oise, south of St. Quentin, against which von Hutier's huge army had been concentrated, was only held by 4 divisions. More than 500,000 Germans were about to attack the 160,000 British under Gough and Byng, whilst from the outset of the battle, large enemy reserves swelled the number of the attacking divisions to 64, i.e., more than the total number of British divisions in France. In all, no less than 1,150,000 Germans were engaged in these tremendous onslaughts. During the five nights which preceded the attack, the German divisions had been brought up secretly, the artillery having previously taken up its positions and corrected its range, without augmenting the volume of firing, so that nothing revealed the increased number of the batteries.