In the meantime, Barclay was led to change his plan, from learning the danger to which Prince Bagration was exposed. The camp at Drissa became too distant a point of junction, and there was every risk that the whole body of the French army, which was now getting itself into motion, would force a passage across the Dwina at Witepsk, a good deal higher up than Drissa, and thus at once turn Barclay's left flank, and entirely separate him from Bagration and his corps d'armée. Alarmed at this prospect, Barclay evacuated the camp, and began to ascend the right side of the Dwina, by Polotsk, towards Witepsk. This line of movement converged with that of Bagration's retreat, and served essentially to favour the desired junction of the two Russian armies. Witgenstein was left near Drissa to observe the enemy, and cover the road to St. Petersburgh. The army first arrived at Polotsk, when the Emperor Alexander left the troops and hastened to Moscow, to recommend and enforce energetic measures, and solicit the heavy sacrifices which the emergency demanded. Barclay continued his march upon Witepsk, hoping to get into communication with Bagration, to whom he had sent orders, directing him to descend the Dnieper as far as Orcsa (or Orcha,) which is about fifty-six wersts from Witepsk. At this period Napoleon was directing his whole reserved forces upon the same point of Witepsk, with a purpose as anxious to prevent the junction of the two Russian armies, as that of Barclay to accomplish that important movement. Had Napoleon's march commenced earlier, there can be no doubt that he must have attained the disputed position sooner by marching from Wilna, than Barclay could have reached it by ascending the Dwina from Drissa. Hasting from Wilna upon the 4th, he might easily have reached Witepsk on the 20th, and would then have found himself, with a chosen army of 120,000 men, without an enemy on his front, posted between the two hostile armies, each of which was pressed by a force superior to their own, and having their flanks and communications at his mercy. Instead of this advantageous condition, the Emperor found himself in front of the grand army of Russia, in a situation where they could not easily be brought to action, although severe and bloody skirmishes took place between the cavalry on both sides.