Banja Luka fell to the Ottomans in 1527. It became the seat of the Sanjak of Bosnia some time prior to 1554, until 1580 when the Bosnia Eyalet was established. Bosnian beylerbeys were seated in Banja Luka until 1639. Ferhad Pasha Sokolović, a relative of Grand Vizier Mehmed-pasha Sokolović, had upon his return to Bosnia in 1574, begun the building of over 200 buildings ranging from artisan and sales shops to wheat warehouses, baths and mosques. Among more important commissions were the Ferhadija and Arnaudija mosques during whose construction plumbing infrastructure was laid out, that served surrounding residential areas. This stimulated the economic and urban development of Banja Luka, which soon became one of the leading commercial and political centres in Bosnia. It was also the central sanjak in the Bosnia Eyalet. In 1688, the city was burned down by the Austrian army, but it quickly recovered. Later periodic intrusions by the Austrian army stimulated military developments in Banja Luka, which made it into a strategic military centre. Orthodox churches and monasteries near Banja Luka were built in the 19th century. Also, Sephardic Jews and Trappists migrated to the city in the 19th century and contributed to the early industrialisation of the region by building mills, breweries, brick factories, textile factories and other important structures.