Again because of the road, the Haskovo area was one of the Bulgarian outlying parts south of the Balkan Range which were first to experience the horror of the devastating invasions of the Ottomans in the 1330s and 40s. With the seizure of Edirne (1369) and especially after the Battle at Chernomen (1371) the Ottomans strengthened their positions in Eastern and Northern Thrace. This put an end to the flourishing and the brilliant material and spiritual values created by the Second Bulgarian State. For the Bulgarian population in Haskovo region came the hardest times. In an attempt to preserve the Bulgarian will and spirit, the bold attacks by haidouk bands became more frequent, the legends about the glorious haidouks such as Angel Voivode, Kralyu Voivode, капитан Петко войвода, etc. were born. They defended the name and honor of the people.       

    Medieval Haskovo appealed to the conquerors with its location and natural conditions. A large part of them settled here permanently. Administratively Haskovo and its district belonged to Chirmen sanjak. The Bulgarian medieval city expanded north of the locality of Yamacha, spread down to the plain and over the years occupied both banks of the river, around the present-day city garden and the residential districts with the Holy Virgin Church and St. Archangels Michael and Gabriel Church, built much later. Another part, the Muslim population, settled around the present-day centre of the city, where the earliest mosque on the Balkans was built, Medjid Mosque (1395).

    The Ottoman conquerors proclaimed the medieval settlement Marsa a “has”, from where its present-day name derived. The hases were large feudal estates, granted to the Ottoman ruling top. According to a record of 1526, Haskovo was the fourth most profitable has of the seven cities in Chirmen sanjak. In nearly all official Turkish documents the city was registered as district Uzunje abad Haskoi. In this case, the name of the Uzundjovo village was used to determine the geographical location of Haskovo, to distinguish it from the homonymous city of Haskoi in Eastern Thrace.

    Gradually, population from the surrounding villages and the Rhodopes came to the city and new Bulgarian neighbourhoods sprang up. Alongside the cultivation of crops, the crafts developed. The need of a city marketplace arose. By 1513 the marketplace at Haskovo was completely formed and placed under the imperial laws. The collected market tax (bac) shows the city marketplace at the close of the 16th century was so large that the annual bac collected from it was a major item in the income of the has owner. In the next centuries the Haskovo market grew and became a stimulant for the development of the Uzundjovo marketplace, which became one of the largest fairs in the Empire.

    Originating in the 18th century, it was fateful to the development of the city till the Liberation. The fair was not only important for the prosperity of Haskovo, and hence the economic life in the Bulgarian lands, but also for the final integration of Turkey into the system of the European and world trade.

    The village of Uzundjovo, located very near the city, on the road between the East and the West, with its station became a centre of commercial exchange. A most detailed description of the fair was made by the French scientist Dr. Ami Boue in 1841: “Uzundjovo is a small town of 2000 inhabitants, situated at an equal distance from the Danube, the Aegean and the Black Sea. It is a meeting place for all regions of the Empire. The streets are full of wooden stalls. Theaters in the open, jugglers, tooth-extractors, menagers occupy some of the places and do the same tricks as those at home. But the fair itself is in many ways different from the fairs in the European countries. No public force, no police can be seen at this gathering of 50 thousand people, nevertheless order reigns. Greeks and Bulgarians, Moldavians and Romanians, Turks and Persians, Russians and Austrians, Jews and Christians have gathered here and live in accord, inspired by the only desire to do better deals and make money...” The largest share of participation belonged to Austria, England, France, Russia. The Haskovo traders, of course, were adequately represented. In 1860 they numbered 48 people. Notably, Dobri Genev, Hristodul Valchev Shishmanov, also head of the Bulgarian Parish in town, Hadji Ivancho Minchev, etc. For the demands of the fair, the produce of Haskovo craftsmen grew. It left the circle of city exchange to go to the markets in the Empire and outside it.