As fortune turned against him, he became ever more nervous about Leipzig. Yet, for the present, the northward march of Blücher rivetted his attention. It puzzled him. Even as late as October 2nd he had not fathomed Blücher's real aim[369]. But four days later he heard that the Prussian leader had crossed the Elbe. At once he hurried north-west with the Guard to crush him, and to resume the favourite project of threatening Berllin and join hands with Davoust. Charging St-Cyr with the defence of Dresden, and Murat with the defence of Leipzig, he took his stand at Düben, a small town on the Mulde, nearly midway between Leipzig and Wittenberg. Thence he reinforced Ney's army, and ordered that Marshal northwards to fall on the rear of Bernadotte and Blücher; while he himself waited in a moated castle at Düben to learn the issue of events. The saxon Colonel, von Odeleben, has left us a vivid picture of the great man's restlessness during those four days. Surrounded by maps and despatches, and waited on by watchful geographer and apprehensive secretary, he spent much of the time scrawling large letters on a sheet of paper, uneasily listening for the tramp of a courier. In truth, few days of his life were more critical that those spent amidst the rains, swamps, and fogs of Düben. Could he have caught Bernadotte and Blücher far apart, he might have overwhelmed them singly, and then have carried the war into the heart of Prussia. But he knows that Dresden and Leipzig are far from safe. The news from that side begins to alarm him: and though, on the north, Ney, Bertrand, and Reynier cut up the rearguard of the allies, he learns with some disquiet that Blücher is withdrawing westwards behind the River Saale, a move which betokens a wish to come into touch with Schwarzenberg near Leipzig. Yet this disconcerting thought spurs him on to one of his most daring designs. "As a means of upsetting all their plans, I will march to the Elbe. There I have the advantage, since I have Hamburg, Magdeburg, Wittenberg, Torgau, and Dresden."[370] What faith he had in the defensive capacities of a great river line dotted with fortresses! His lieutenants did not share it. Caulaincourt tells us that his plan of dashing at Berlin roused general consternation at headquarters, and that the staff came in a body to beg him to give it up, and march back to protect Leipzig. Reluctantly he abandons it, and then only to change it for one equally venturesome. He will crush Bernadotte and Blücher, or throw them beyond the Elbe, and then, himself crossing the Elbe, ascend its right bank, recross it at Torgau, and strike at Schwarzenberg's rear near Leipzig.