At length a reinforcement of four thousand dragoons arriving, he fell upon the Swedes a third time; who retreated to a small town called Prospock, where they were again attacked; they then marched towards the Desna, the Russians still pursuing them: yet they were never broken, but lost upwards of eight thousand men, seventeen pieces of cannon, and forty-four colours: the czar took fifty-six officers and near nine hundred private men prisoners; and the great convoy of provisions and ammunition that were going to Charles's army, fell into the hands of the conqueror. This was the first time that the czar in person gained a pitched battle, against an enemy who had distinguished himself by so many victories over his troops: he was employed in a general thanksgiving for his success, when he received advice that general Apraxin had lately gained an advantage over the enemy in Ingria, (Sept. 17,) some leagues from Narva, an advantage less considerable indeed than that of Lesnau; but this concurrence of fortunate events greatly raised the hopes and courage of his troops. Charles XII. heard of these unfortunate tidings just as he was ready to pass the Desna, in the Ukraine. Mazeppa at length joined him; but instead of twenty thousand men, and an immense quantity of provisions, which he was to have brought with him, he came with only two regiments, and appeared rather like a fugitive applying for assistance, than a prince, who was bringing powerful succours to his ally. This Cossack had indeed begun his march with near fifteen or sixteen thousand of his people, whom he had told, at their first setting out, that they were going against the king of Sweden; that they would have the glory of stopping that hero on his march, and that he would hold himself eternally obliged to them for so great a service. But when they came within a few leagues of the Desna, he made them acquainted with his real design. These brave people received his declaration with disdain: they refused to betray a monarch, against whom they had no cause of complaint, for the sake of a Swede, who had invaded their country with an armed force, and who, after leaving it, would be no longer able to defend them, but must abandon them to the mercy of the incensed Russians, and of the Poles, once their masters, and always their enemies: they accordingly returned home, and gave advice to the czar of the defection of their chief: Mazeppa found himself left with only two regiments, the officers of which were in his own pay.