On his arrival there, on July 8th, this hope also was dashed. Michaud, a young Sardinian engineer, pointed out several serious defects in their construction. Barclay also protested against shutting up a large part of the defending army in a camp which could easily be blockaded by Napoleon's vast forces. Finally, as the Russian reserves stationed there proved to be disappointingly weak both in numbers and efficiency, the Czar determined to evacuate the camp, intrust the sole command to Barclay, and retire to his northern capital. It is said that, before he left the army, the Grand Duke Constantine, a friend of the French cause, made a last effort to induce him to come to terms with Napoleon, now that the plan of campaign had failed. If so, Alexander repelled the attempt. Pride as a ruler and a just resentment against Napoleon prevented any compromise; and probably he now saw that safety for himself and ruin for his foe lay in the firm adoption of that Fabian policy of retreat and delay, which Scharnhorst had advocated and Barclay was now determined to carry out. Though still hampered by the intrigues of Constantine, Bennigsen, and other generals, who hated him as a foreigner and feigned to despise him as a coward, Barclay at once took the step which he had long felt to be necessary; he ordered a retreat which would bring him into touch with Bagration. Accordingly, leaving Wittgenstein with 25,000 men to hold Oudinot's corps in check on the middle Dwina, he marched eastwards towards Vitepsk. True, he left St. Petersburg open to attack; but it was not likely that Napoleon, when the summer was far spent, would press so far north and forego his usual plan of striking at the enemy's chief forces. He would certainly seek to hinder the junction of the two Russian armies, as soon as he saw that this was Barclay's aim. Such proved to be the case. Napoleon soon penetrated his design, and strove to frustrate it by a rapid move from Vilna towards Polotsk on Barclay's flank, but he failed to cut into his line of march, and once more had to pursue.