In the case of Salonika, which had been recently sold by the Greek Emperor to the Republic of Venice, now desirous of effecting a lodgment in Macedonia, Murad refused to recognize the right of the Emperor to transfer to a foreign Power a city which at one time had been under Ottoman rule. It had three times in the last hundred years been captured by the Ottomans, and had as often been recaptured by the Greeks. Murad led an army, in 1430, to attack it, and, after a vigorous resistance by the Venetians, captured it by assault, and finally annexed the city and its district to the Turkish Empire. It was thought that Murad showed great clemency in not allowing his soldiers to indulge in a wholesale massacre. The Greek inhabitants, however, were sold into slavery, and their numbers were so great that a good-looking girl was sold for the price of a pair of boots. The suppression of rebellion in Asia Minor, the subjection of the Greek Emperor to the position of a humble vassal, and the capture of Salonika had occupied Murad for some years. Later he was involved in long struggles with his neighbours, the Hungarians, on the northern boundaries of his Empire. The Ottomans were engaged in constant raids across the Danube, where vast districts were devastated, and thousands of their population were carried off as captives for sale as slaves. There arose about this time in Hungary a national hero, the celebrated Hunyadi, a natural son of the late King Sigismund. He was a born leader of men, not a great general, but a most valiant fighter. He had gained great distinction in war in other directions. He now became the soul of hostility against the Ottomans. He was known as the White Knight, on account of his silver armour, which always shone in the van of the impetuous charges of his cavalry. He was rightly regarded by his countrymen as a patriot and a national hero. None the less, he was a bloodthirsty ruffian. He made a practice of massacring all the prisoners taken in battle. He found pleasure in having this effected, in his presence, at banquets, where the guests were entertained by the shrieks of the dying men. Hunyadi for twenty years was a terror to the Ottoman armies. His first encounter with them was at Hermannstadt, north of the Danube, which was invested by an army of eighty thousand Ottomans. He led an army of twenty thousand Hungarians against them, in relief of the fortress, and inflicted a severe defeat on them, in despite of great disparity of numbers. Twenty thousand of the Ottomans were killed, including the general. The others were dispersed. Murad sent another army of eighty thousand men against him, under another Pasha. Hunyadi again defeated it with great slaughter at Varsag.