On his way he received tidings that the Crimean Tatars had come plundering into Russia, probably thinking to attack Moscow, while Ivan was besieging Kazan. He at once sent off the Prince Kourbsky with 15,000 men, who met double that number of Tatars at Toula, and totally defeated them, pursuing them to the River Chevorona, where, after a second defeat, they abandoned a great number of Russian captives, and a great many camels. Prince Kourbsky was wounded in the head and shoulder, but was able to continue the campaign. Some of the boyards murmured at the war, and declared that their strength and resources were exhausted. Upon this the Tzar desired that two lists might be drawn up of the willing and unwilling warriors in his camp. 'The first', he said, 'shall be as dear to me as my own children; their needs shall be made known to me, and I will share all I have with them. The others may stay at home; I want no cowards in my army.' No one of course chose to be in the second list, and about this time was formed the famous guard called the Strelitzes, a body of chosen warriors who were always near the person of the Tzar. In the middle of August, 1552, Ivan encamped in the meadows on the banks of the Volga, which spread like a brilliant green carpet around the hill upon which stood the strongly fortified city of Kazan. The Tatars had no fears. 'This is not the first time', they said, 'that we have seen the Muscovites beneath our walls. Their fruitless attacks always end in retreats, till we have learned to laugh them to scorn;' and when Ivan sent them messengers with offers of peace, they replied, 'All is ready; we only await your coming to begin the feast.' They did not know of the great change that the last half-century had made in sieges. One of the Italian condottieri, or leaders of free companies, had made his way to Moscow, and under his instructions, Ivan's troops were for the first time to conduct a siege in the regular modern manner, by digging trenches in the earth, and throwing up the soil in front into a bank, behind which the cannon and gunners are posted, with only small openings made through which to fire at some spot in the enemy's walls. These trenches are constantly worked nearer and nearer to the fortifications, till by the effect of the shot an opening or breach must be made in the walls, and the soldiers can then climb up upon scaling ladders or heaps of small faggots piled up to the height of the opening. Sometimes, too, the besiegers burrow underground till they are just below the wall, then fill the hole with gunpowder, and blow up all above them; in short, instead of, as in former days, a well- fortified city being almost impossible to take, except by starving out the garrison, a siege is in these times almost equally sure to end in favor of the besiegers.