Complex sentence: In the Ottoman Empire of the 17th century the "yerliyya" were local Janissaries that had been sent to an urban centre many years earlier and had become fully integrated into their surroundings, often playing important roles in the commercial and political life of the area.
Split into simpler sentences: In the Ottoman Empire of the 17th century the "yerliyya" was a term used to describe local Janissaries. These were Janissaries that had been sent to an urban centre many years ago and had become fully integrated into their surroundings, often playing important roles in the commercial and political life of the area.