Unfortunately for the success of this plan, although the Eleventh Corps performed its function and drew the Russian army with it in its retreat toward Erzerum, the Ninth and Tenth Corps suffered a reverse and were compelled to fall back also. Similarly, the Third Corps was compelled to yield before superior numbers and barely escaped envelopment. Naturally, there is considerable difference of opinion as to the question of numbers involved in these operations. It seems to be fairly well established, however, that the Russians used, roughly, eight army corps, or slightly more than 300,000 men. Eight corps are known to have been at the disposal of the grand duke, but a small portion of his force was at the same time engaged in an expedition into northern Persia, so that the round figures given would seem to be conservative. Although but four Turkish corps are mentioned, it is known that the Ottoman command had at its disposal considerable numbers of Kurds, Persians, Arabs, and other irregular troops, as well as several units not specifically mentioned in the official accounts. Thus the estimate of 180,000 to 200,000 men would not seem to be out of the way. While the thrusts from the northeast and southeast were fighting their way toward the flanks of Erzerum, the Russian troops advancing along the Kars-Erzerum road, driving the Eleventh Corps before them, made a fierce frontal assault upon the outer forts of the town. In this connection it would be well to examine more minutely the conditions that confronted the Russian commander. Erzerum is situated on a plateau some 6,000 feet above sea level, and the key forts had been placed on high ground commanding the surrounding country. However well the Russian transport department had done its work, the Russian supply of heavy artillery could not have been overwhelming in the sense that heavy guns were overwhelming on other fronts. There could, therefore, have been no condition of affairs where the infantry was called upon simply to occupy positions previously shattered by gunfire. Indeed, the best opinions agree that little or no real damage was done by the artillery to the Erzerum forts and that the infantry had to advance against practically intact defenses. Yet, after five days of fierce assault, the hardy Siberian troops of General Judenich's army carried nine of the outlying forts and forced the evacuation of the entire fortress.