The revolt, which began in September 869, was concentrated in the districts of Iraq and al-Ahwaz (modern Khuzestan Province) in the central regions of the Abbasid Caliphate. Over the course of the next fourteen years, the Zanj were able to combat the superior arms of the Abbasid government by waging guerrilla warfare against their opponents. They became adept at raiding towns, villages and enemy camps (often at night), seizing weapons, horses, food and captives and freeing fellow slaves, and burning the rest to cinders to delay retaliation. As the rebellion grew in strength, they also constructed fortresses, built up a navy for traversing the canals and rivers of the region, collected taxes in territories under their control, and minted their own coins.