At the beginning of the 17th century, during the uprising led by the name of Bocskai István, the armed social group, then already known as the Hajdú, gained decisive influence as the men at arms of Bocskai and the later Transylvanian princes. The Transylvanian princes first settled the Hajdú communities in the settlements of Szabolcs County, then in the Bihar County. These groups were called to fight by the commander of Nagyvárad (Oradea). Berettyóújfalu also became one of the links of the defensive ring around the castle of Nagyvárad, which was formed by the Hajdú settlements, following that Prince Báthory Gábor donated the estates of Berettyóújfalu and Szentkozma to Captain Nadányi Gergely and his hundred soldiers in 1608. The integration did not always go smoothly, and the original inhabitants did not enjoy the privileges that the Hajdús had. It took more than a hundred years and a circumstance that affected all the people living here. Towards the end of the Great Turkish War (1683-1699), the increasingly established administration challenged the privileges which the Hajdú townships had gained from the princes of Transylvania and which had been confirmed on several occasions by the King of Hungary. The privileged areas (Jász, Kun and Hajdú communities) came under increasing pressure and in the early 1700s they lost the exemptions they had received in return for their military service. This was also the fate of most of the Hajdú townships in Bihar. More than a dozen of them, including Berettyóújfalu, fell into the hands of Palatine Esterházy Pál in exchange for the lost salary. The Hajdú townships had been complaining about the loss of their rights for a long time, thus it is no wonder that they were among the first to take up arms on the side of Rákóczi Ferenc II. After the defeat of the War of Independence, all hopes were dashed that the glory of these settlements would be restored. It was only in the second half of the 19th century, in 1865, when the former Hajdú towns belonging to the Esterházy family’s Derecske manor were able to escape these burdensome circumstances. Even after the demise of the manor, the old world could not be restored, as the administrative regulations following the Austro-Hungarian Compromise degraded the former market towns to large villages, losing all previous privileges and integrating them into the structure of the country.