During the Karamanian campaign, Murad adopted the policy of treating non-combatants in a friendly fashion. Strict orders were given to refrain from violence and looting. Murad hoped to win the Karamanlis by kindness, and to pave the way for a later assimilation. It was the first campaign undertaken against fellow Moslems. The Serbian contingent, who cared nothing for the success of this policy, and who claimed that they had been promised booty in return for their services, did not obey the order. A number of them were summarily executed.[397] When the survivors returned to their homes in the spring of 1388, they complained bitterly of the way they had been treated, and declared that service in the Ottoman army, for the Christian all risk and no gain, was nothing less than a slavery leading to death. This discontent gave Lazar the opportunity for which he had long been looking. He decided to profit by the resentment of the Serbians against Murad,[398] and make a supreme effort to free Serbia from the menace of the Ottoman yoke, which had grown very real since the capture of Nish. The Slavs of upper Serbia and of Bosnia realized the imminence of an Ottoman invasion, and they were now ready--or at least they appeared to be ready--to rally around Lazar. Up to this time the Serbians had never recognized Lazar as the leader of the race. The pan-Serbian alliance was made possible by the adhesion of Tvrtko, kral of Bosnia. He had come into prominence after the battle of Cernomen as a supporter of Lazar against the sons of Vukasin and other Serbian chieftains who were dissatisfied with the election of Lazar. But in return for his aid, he got under his control a large part of upper Serbia, including Milesevo, which was the burial-place of St. Sava, apostle to the Serbians. In 1376, he crowned himself ‘king of Bosnia and Serbia’ on the tomb of St. Sava, placing upon his head the two crowns, and changing his name to Stephen. Neither Louis of Hungary nor Lazar was consulted by Tvrtko, and he took no measures to secure their assent to his pretensions. After his coronation, he conquered Cattaro, and fought successfully with Balza of Albania.[399]