Murad gladly gave his new ally and brother-in-law a strong Ottoman army to co-operate in the attack upon the Hungarians. The Osmanlis helped in driving Louis out of Widin. Sisman, like Cantacuzenos, first guided the Osmanlis through the heart of his country. It was under the leadership of Sisman that they saw the Danube, their river of destiny. When Sisman, even with the help of the Osmanlis and Wallachians, could not gain possession of Stracimir’s inheritance, he returned to Tirnovo. There he learned that Lalashahin was planning an expedition westward, which seemed to be intended against Sofia. Sisman now realized that his position was critical and that the fate of Bulgaria was at stake. In the early spring of 1371, he hurried into the Rilo Mountains and sent out an appeal to the Serbian kral who was at that time ruling in eastern Macedonia. Then he went to the relief of Ishtiman, which was already menaced by the Osmanlis. Failing in this effort, Sisman fell back to Samakov, where he was joined by the Serbians. Lalashahin led his army from Ishtiman into the valley of the Isker. The two krals joined battle with him in the plain of Samakov. The Ottoman victory was decisive.[319] The Serbians and Bulgarians fled into the recesses of Musalla, the highest mountain in the Balkan peninsula, and of Popova Shapka. Sisman disappeared after the battle.[320] The way to Sofia was open. All Bulgaria lay at the feet of the conqueror. It is from the battle of Samakov that we must date the destruction of an independent Bulgaria. But Murad was not yet ready to follow up this decisive victory. The only immediate result of the battle of Samakov was the submission of Constantine, Bulgarian prince of Kustendil, in the upper valley of the Struma. After the fall of Samakov, his position was untenable. Constantine hurried to Murad’s camp, and did homage to the conqueror. Murad gave back to him as vassal his principality.[321] With the wisdom that marked every successive step of his progress in Europe, Murad refrained from advancing beyond Samakov. He ordered Lalashahin to lead the army into Macedonia, and to join Evrenos in the advance towards the Vardar. IX