In the winter of 1345 a diet of the kingdom proclaimed Stephen Dušan emperor of the Serbs and the Greeks, and in the following Easter (April 16, 1346) the patriarchs of Serbia and Bulgaria crowned him “in Constantinopolitan empire”. Even before that, the archbishopric had been elevated to a patriarchate. The undertakings continued to unite all the Byzantine provinces under his scepter. In 1350 Thessaly and Epirus were conquered, with which the limits of the state were brought from the Danube and the Bulgarian borders to the lower Adriatic and Olympus. Legal life was regulated, with the compilation of the first Serbian code of laws (Du š anov Zakonik), promulgated in the diets of 1349 and 1354. When the work was about to be completed, Dušan died suddenly on December 20, 1355, at the age of 48. Serbia as an empire, conceived, felt, prepared, but not realized, has virtually only one decade of life: from 1345 to 1355.
The state that Dušan had put together, despite being territorially extensive and militarily strong, had such inherent weaknesses as to be, even without external pitfalls, doomed to dissolution. Above all, he lacked a ruling class that had the conscience and discipline of government. The dynasts, magnates, courtiers and nobles sent to the government of the newly acquired regions, did not go there with the spirit of administrators, but of meritorious crowns, donated by kingdoms and cities, dismissed by the emperor and promoted to sovereigns. Growing up in the atmosphere of dynastic struggles, their study was solely aimed at achieving greater autonomy, increasing their power, overwhelming each other and, if it were ever possible, aspire to the same royal and imperial crown.
Thus, when Dušan died, and the weak and inept Uroš IV succeeded him, bitter and dissolving internal struggles broke out throughout the empire. Uroš took a back seat and in the whirlwind of competitions a certain Vukašin came to light, who since 1366 bears the title of king, appears corrector of Uroš, but in fact is the only master of the state. External offensives were added to the internal disintegration: in 1359 Louis of Hungary took Macsó and Belgrade. The most dangerous enemy, however, were the Turks who, having begun the passage in the Balkan in 1352, arrived in Adrianople in 1366 and proceeded strong, numerous and threatening. Vukashin had to face them. On September 26, 1371 in Černomjan, on the Maritza river, a first terrible battle took place in which the Serbian army was almost annihilated and Vukašin lost his life. Macedonia and the southern provinces became tributaries of the Turks who did not hold back from advancing north. After two months, Uroš also died. With this Serbia can be considered finished. However, a shadow of a state survived until the armies of King Lazarus Hrebeljanović, who succeeded Vukašin, and Stefano Tvarco (Tvrtko) of Bosnia, who in 1377 had also been crowned king of Serbia, were not once again destroyed in the memorable battle of Kosovo, on the day of St. Vitus 1389. King Lazarus and the sultan fell on the field.