The young prince set out that same day with Li tsi, a state minister, but as the attack was continued, the Kin ruler indignant at Mongol duplicity gave the signal for action. Subotai had set up an immense line of catapults and hurled large, jagged millstones with dreadful impetus. At the end of some days of ceaseless hurling, stones were piled up at points almost to the top of the ramparts; the towers, though built of strong timber from old palaces, were broken. To deaden the effect of these millstones the towers were backed with huge bags filled with wheat-straw, and horse dung, covered with felt and tied with cords very firmly, also planks faced with untanned hides of buffaloes. The Mongols hurled fire with ballistas to burn the defences. No projectile, however, could injure those strange massive walls of the fortress, which were mainly of clay grown as solid as iron. The besieged made use of inflammable projectiles, that is, iron pots filled with powder of some kind. These pots hurled out by ballistas or let down by strong chains burst with great noise, maiming men or destroying them a hundred feet from the place of explosion. Attack and defence were original and vigorous. Some of the Mongols, well shielded by raw hides of buffalo, approached, dug holes in the walls and remained there at work safe from all missiles. The besieged hurled spears carrying fireworks which exploding burned everything within thirty feet of them. These two kinds of projectiles were greatly feared by the Mongols. After assaults which continued sixteen days, almost without interval, during which time it was said, though of course incorrectly, that a million of men fell, Subotai sent a message declaring that as discussions for peace were in progress hostilities would cease altogether, and he prepared to withdraw to some distance. The Emperor in answer sent rich parting presents to the Mongol general and his officers. One month after this truce a plague broke out in the capital, and during fifty days coffins to the number of nine hundred thousand, as the account runs, were borne from the city; besides there were corpses of indigent people which were put in the earth without coffins or boxes. During discussions for peace, a Mongol envoy, Tang tsing, with a suite of thirty persons, was slain in Pien king by the populace. This deed went unpunished and unnoted by the Chinese, hence command was given Subotai to attack the Kin capital a second time. Ogotai had also another complaint against the Kin sovereign: Nin kia su had taken into his service, and even rewarded, a general of the Mongols who, not enduring his chief, had passed to the Kin side and yielded up cities which were under his control.