In 1340 the Turks had begun to ravage the valley of the Maritza; in 1362 they captured Philippopolis, and in 1382 Sofia. In 1366 Ivan Shishman III., the last Bulgarian tsar, was compelled to declare himself the vassal of the sultan Murad I., and to send his sister to the harem of the conqueror. In 1389 the rout of the Servians, Bosnians and Croats on the famous field of Kossovo decided the fate of the Peninsula. Shortly afterwards Ivan Shishman was attacked by the Turks; and Trnovo, after a siege of three months, was captured, sacked and burnt in 1393. The fate of the last Bulgarian sovereign is unknown: the national legend represents him as perishing in a battle near Samakov. Vidin, where Ivan's brother, Strazhimir, had established himself, was taken in 1396, and with its fall the last remnant of Bulgarian independence disappeared.
The five centuries of Turkish rule (1396-1878) form a dark epoch in Bulgarian history. The invaders carried fire and sword through the land; towns, villages and monasteries were sacked and destroyed, and whole districts were converted into desolate wastes. The inhabitants of the plains fled to the mountains, where they founded new settlements. Many of the nobles embraced the creed of Islam, and were liberally rewarded for their apostasy; others, together with numbers of the priests and people, took refuge across the Danube. All the regions formerly ruled by the Bulgarian tsars, including Macedonia and Thrace, were placed under the administration of a governor-general, styled the beylerbey of Rum-ili, residing at Sofia; Bulgaria proper was divided into the sanjaks of Sofia, Nikopolis, Vidin, Silistria and Kiustendil. Only a small proportion of the people followed the example of the boyars in abandoning Christianity; the conversion of the isolated communities now represented by the Pomaks took place at various intervals during the next three centuries. A new kind of feudal system replaced that of the boyars, and fiefs or spahiliks were conferred on the Ottoman chiefs and the renegade Bulgarian nobles.
The Christian population was subjected to heavy imposts, the principal being the haratch, or capitation-tax, paid to the imperial treasury, and the tithe on agricultural produce, which was collected by the feudal lord. Among the most cruel forms of oppression was the requisitioning of young boys between the ages of ten and twelve, who were sent to Constantinople as recruits for the corps of janissaries. Notwithstanding the horrors which attended the Ottoman conquest, the condition of the peasantry during the first three centuries of Turkish government was scarcely worse than it had been under the tyrannical rule of the boyars. The contemptuous indifference with which the Turks regarded the Christian rayas was not altogether to the disadvantage of the subject race. Military service was not exacted from the Christians, no systematic effort was made to extinguish either their religion or their language, and within certain limits they were allowed to retain their ancient local administration and the jurisdiction of their clergy in regard to inheritances and family affairs.
At the time of the conquest certain towns and villages, known as the voïnitchki sela, obtained important privileges which were not infringed till the 18th century; on condition of furnishing contingents to the Turkish army or grooms for the sultan's horses they obtained exemption from most of the taxes and complete self-government under their voïvodi or chiefs. Some of them, such as Koprivshtitza in the Sredna Gora, attained great prosperity, which has somewhat declined since the establishment of the principality. While the Ottoman power was at its height the lot of the subject-races was far less intolerable than during the period of decadence, which began with the unsuccessful siege of Vienna in 1683. Their rights and privileges were respected, the law was enforced, commerce prospered, good roads were constructed, and the great caravans of the Ragusan merchants traversed the country. Down to the end of the 18th century there appears to have been only one serious attempt at revolt - that occasioned by the advance of Prince Sigismund Báthory into Walachia in 1595. A kind of guerilla warfare was, however, maintained in the mountains by the kaiduti, or outlaws, whose exploits, like those of the Greek klepkts, have been highly idealized in the popular folk-lore. As the power of the sultans declined anarchy spread through the Peninsula. In the earlier decades of the 18th century the Bulgarians suffered terribly from the ravages of the Turkish armies passing through the land during the wars with Austria. Towards its close their condition became even worse owing to the horrors perpetrated by the Krjalis, or troops of disbanded soldiers and desperadoes, who, in defiance of the Turkish authorities, roamed through the country, supporting themselves by plunder and committing every conceivable atrocity.
After the peace of Belgrade (1737), by which Austria lost her conquests in the Peninsula, the Servians and Bulgarians began to look to Russia for deliverance, their hopes being encouraged by the treaty of Kuchuk Kaïnarji (1774), which foreshadowed the claim of Russia to protect the Orthodox Christians in the Turkish empire. In 1794 Pasvanoglu, one of the chiefs of the Krjalis, established himself as an independent sovereign at Vidin, putting to flight three large Turkish armies which were despatched against him. This adventurer possessed many remarkable qualities. He adorned Vidin with handsome buildings, maintained order, levied taxes and issued a separate coinage. He died in 1807. The memoirs of Sofronii, bishop of Vratza, present a vivid picture of the condition of Bulgaria at this time. "My diocese," he writes, "was laid desolate; the villages disappeared - they had been burnt by the Krjalis and Pasvan's brigands; the inhabitants were scattered far and wide over Walachia and other lands."