Upon receipt of these orders Baird advanced again to Astorga and, on the 20th December, joined Moore at Mayorga. He took with him all available battalions, but some were still in rear, since the Spanish authorities had been unable to provide transport or provisions on the road for any but small bodies of troops moving at intervals of some days. The 51st Regiment, forming part of Leith's Brigade, was still far behind, and did not come into the zone of operations until the eventual retreat was in full swing. Moore, however, now had sufficient men for his purpose, for he knew that Soult's force was in numbers inferior to his own; and the operations at once commenced by a brilliant cavalry action, in which Paget, with 400 British sabres, routed 600 of the French cavalry at Sahagun. Soult was now known to be at Saldanha and Carrion, and Moore decided to halt his force for forty-eight hours in order to allow the rear divisions to close up, and then to attack at dawn on the 24th December. On the night of the 23rd-24th the troops set out on the march which was to bring them at daylight before the bridge of Carrion, but they had not marched far before they received the unwelcome order to retrace their steps and return to their bivouacs at Sahagun. Moore had received information which upset all his calculations; the scheme which he had devised for drawing Napoleon's armies after him had worked only too successfully, for he learned that Napoleon was already in full march upon him, and that within a few hours the situation of the British army might become critical. He determined, therefore, to abandon the attack on Soult and endeavour to carry out his original programme by withdrawing to his ships before Napoleon's masses should fall upon him. That Christmas day was spent by the disappointed army in making the second march of the long and arduous retreat to Corunna.