The Grand Duke had now only to prepare for resistance, and this he did with that determination and coolness of which, under other circumstances, he had given incontestable proofs. The news of the taking of Ichim, Omsk, and Tomsk, successively reached Irkutsk. It was necessary at any price to save the capital of Siberia. Reinforcements could not be expected for some time. The few troops scattered about in the provinces of Siberia could not arrive in sufficiently large numbers to arrest the progress of the Tartar columns. Since therefore it was impossible for Irkutsk to escape attack, the most important thing to be done was to put the town in a state to sustain a siege of some duration. The preparations were begun on the day Tomsk fell into the hands of the Tartars. At the same time with this last news, the Grand Duke heard that the Emir of Bokhara and the allied Khans were directing the invasion in person, but what he did not know was, that the lieutenant of these barbarous chiefs was Ivan Ogareff, a Russian officer whom he had himself reduced to the ranks, but with whose person he was not acquainted. First of all, as we have seen, the inhabitants of the province of Irkutsk were compelled to abandon the towns and villages. Those who did not take refuge in the capital had to retire beyond Lake Baikal, a district to which the invasion would probably not extend its ravages. The harvests of corn and fodder were collected and stored up in the town, and Irkutsk, the last bulwark of the Muscovite power in the Far East, was put in a condition to resist the enemy for a lengthened period. Irkutsk, founded in 1611, is situated at the confluence of the Irkut and the Angara, on the right bank of the latter river. Two wooden draw-bridges, built on piles, connected the town with its suburbs on the left bank. On this side, defence was easy. The suburbs were abandoned, the bridges destroyed. The Angara being here very wide, it would not be possible to pass it under the fire of the besieged. But the river might be crossed both above and below the town, and consequently, Irkutsk ran a risk of being attacked on its east side, on which there was no wall to protect it. The whole population were immediately set to work on the fortifications. They labored day and night. The Grand Duke observed with satisfaction the zeal exhibited by the people in the work, whom ere long he would find equally courageous in the defense. Soldiers, merchants, exiles, peasants, all devoted themselves to the common safety. A week before the Tartars appeared on the Angara, earth-works had been raised. A fosse, flooded by the waters of the Angara, was dug between the scarp and counterscarp. The town could not now be taken by a coup de main. It must be invested and besieged.