Forces of the independent Zulu kingdom inflicted a crushing defeat on British imperial forces at Isandlwana in January 1879. The Zulu Army was not, however, a professional force, unlike its British counterpart, but was the mobilized manpower of the Zulu state. Ian Knight details how the Zulu army functioned and ties its role firmly to the broader context of Zulu society and culture. The Zulu army had its roots in the early groups of young men who took part in combats between tribes, but such warfare was limited to disputes over cattle ownership, grazing rights, or avenging insults. In the early nineteenth century the Zulu nation began a period of rapid expansion, and King Shaka began to reform his forces into regular military units. Ian Knight charts the development and training of the men that formed the impi which later operated so successfully under King Cetshwayo. He analysis the Zulu's fighting methods, weapons and philosophy, all of which led to the disciplined force that faced the British army in 1879.