The allies, who had in their latest councils wound up their resolution to the decisive experiment of marching on Paris, were at first at a loss to account for Napoleon's disappearance, or to guess whither he had gone. This occasioned some hesitation and loss of time. At length, by the interception of a French courier, they found despatches addressed by Buonaparte to his government at Paris, from which they were enabled to conjecture the real purpose and direction of his march. A letter,[14] in the Emperor's own hand, to Maria Louisa, confirmed the certainty of the information.[15] The allies resolved to adhere, under this unexpected change of circumstances, to the bold resolution they had already formed. To conceal the real direction of his march, as well as to open communications with the Silesian army, Schwartzenberg, moving laterally, transferred his headquarters to Vitry, where he arrived on the 24th, two days after it had been summoned by Napoleon. Blucher, in the meantime, approached his army from Laon to Chalons, now entirely re-organised after the two bloody battles which it had sustained. As a necessary preparation for the advance, General Ducca was left on the Aube, with a division of Austrians, for the purpose of defending their depôts, keeping open their communications, and guarding the person of the Emperor Francis, who did not perhaps judge it delicate to approach Paris in arms, with the rest of the sovereigns, while the city was nominally governed by his own daughter as Regent. Ducca had also in charge, if pressed, to retreat upon the Prince of Hesse-Homberg's army, which was in triumphant possession of Lyons.