Two gleams of light, one of them quickly dimmed and the other distant, relieved the gloom of the last winter of the war. As the Flanders offensive subsided in the mud, Haig was preparing another blow by a different hand in a drier land; and he, too, was working to find an escape from trench-warfare on lines not unlike those of Ludendorff. Both were dissatisfied with the obstacles which intense bombardment, used for initial success, placed in the way of its prosecution; but by one of the ironies of the war, while Ludendorff now relied on the superiority of his human material, Haig looked for success to the greater ingenuity of mechanical contrivance expressed in Tanks. They were under a cloud in Flanders because they could not advance upon mud and water; but on higher ground their improved efficiency and numbers might be used to some effect. The plan adopted contemplated a narrow front but an ambitious objective. It was to break the Hindenburg lines at their nodal point in front of Cambrai. If successful it would disorganize the whole German scheme of defence in the West, and would in any case tend to divert the Germans from their Italian campaign. The objective was not Cambrai itself, but to break through the Hindenburg lines as far as Bourlon and beyond, and then to take them in reverse from Bourlon westwards and northwards to the Sensée and the Scarpe. In other words, it appeared to be an experiment in tactics which might with good fortune develop into a strategical means of achieving from the south of Douai and Lille what the Flanders campaign had failed to secure to the north of them. The German line was thin, and, had it been made of the stuff of the Italian line at Caporetto, Haig might have repeated Ludendorff's unexpected success. There was a third and more sinister explanation of the battle of Cambrai, that it was a practical attempt to answer the gibes in which the Prime Minister had indulged at the tactics of the British Army.