From the 13th century, the two main Balkan powers Byzantium and Bulgaria fell victims to a process of decentralization, as local feudal lords grew stronger and more independent from the emperors in Constantinople and Tarnovo.

In Bulgaria the powerful House of Shishman ruled over the Vidin Province in the west, while in the east Balik established a quasi-independent Despotate of Dobruja.

In 1330 Serbian forces defeated Bulgarian ones, led by Emperor Michail Shishman at Velbazhd effectively raising the country to the status of the most powerful state in the region.

Circa mid 14th century the Balkans were politically disunited into a number of small states frequently in competition with each other and there was no single strong entity with a powerful enough army to withstand the Muslim invaders.

In 1344, Momchil, the independent Bulgarian ruler of the Rhodope and Aegean regions, whose army grew to 2,000 men,[6] took an important role in the Byzantine civil war.

Even though his troops continued the resistance in the Eastern Rhodopes, in May 1345 the Turks led by Umur Beg marched from Asia Minor and devastated Bulgarian territories driving away people and livestock.

Sources attest that the independent ruler perished in the battle without leaving a successor, and with little political will or leadership left to counter the Ottoman invasion.

[12] During the Byzantine civil wars Ivan Alexander regained control over several towns in Thrace and the Rhodopes but his frequent interference in the internal affairs of Byzantium hampered any closer relations between the two counties despite the peace established in 1332.

In 1352 Turkish forces invaded Bulgaria anew, raiding Thrace, particularly the vicinities of Aitos, Yambol, and Plovdiv, and capturing rich spoils.

[15] In 1355 the Ottomans launched a campaign towards Sofia, but were soon engaged by the army of Ivan Alexander's eldest son and heir Michael Asen close to Ihtiman.

[16] The defeat raised serious alert not only in Tarnovo, but also in Constantinople, forcing John Kantakouzenos to abdicate and removing one of the main facilitators of the Ottoman invasion.

[20] Ottoman chronicler Hoca Sadeddin Efendi suggests that Turkish advance between 1359 and 1364 involved destruction and depopulation of many areas: the towns Plovdiv, Stara Zagora, and Sliven were devastated, and others such as Venets and Sotirgrad were completely destroyed.

Serbian brothers Vukashin and Uglesha, respectively the king of Prilep and the despot of Ser, gathered a numerous Christian army aiming to stop the Muslim invaders.

Considerably less numerous troops led by Lala Şahin Pasha attacked the united Balkan forces at night on 26 September as the latter camped by the village of Chernomen in the lower Maritsa valley.

[27] Immediately after the battle, the armies of Murad I embarked on another campaign overrunning Northern Thrace and forcing young Ivan Shishman to pull back north of the Balkan Mountains.

[28] One of Ivan Shishman's voivodes, Shishkin, was killed in battle on the southern skirts of the Balkan Mountains further easing the Ottoman conquest of the Rhodopes, Kostenets, Ihtiman, and Samokov.

They ruled over the entire Thrace and had seized the lands of Uglesha in Eastern Macedonia and managed to subordinate Vukashin's son Marko and Ivan Shishman who became their vassals.

[33] The Rakovitsa fortress (now in ruins) was besieged by Daud Pasha and fiercely defended by its voivoda Kurt; after futile attempts to capture it with force, the Turks agreed to negotiations and the Bulgarians surrendered keeping their property.

[24] Similarly, the population of Tsepina, one of the strategic fortresses of the Rhodopes, resisted Ottoman attacks for nine months before surrendering in return for their lives and property[34] after Daud Pasha cut off the water supplies.

Fighting occurred at Zarenitsa, Zagrad, Gradishte, Chiltepe and Karakulas (along Vacha), Imaretdere and Momina Voda (heights close to Ardino) among others.

With a large army Sultan Murad moved towards the southwestern regions of the Tarnovo Tsardom with the main objective to seize its center Sofia.

[42] While he was absent the Turks managed to infiltrate Sofia and one Muslim Bulgarian captured ban Yanuke while hunting and sent him to Lala Şahin who was in Plovdiv at that time.

The Serbian Prince Lazar and the Bosnian King Tvrtko I organized an anti-Ottoman coalition and the Bulgarian Emperor joined them but was unable to send troops.