Impi warriors were trained as early as age six, joining the army as udibi porters at first, being enrolled into same-age groups (intanga). Until they were buta'd, Zulu boys accompanied their fathers and brothers on campaign as servants. Eventually, they would go to the nearest ikhanda to kleza (which literally means to drink directly from the udder), at which point they would become inkwebane, or cadets. They would spend their time training until the king formally enlisted them. They would challenge each other to stick fights, which had to be accepted on pain of dishonour.
After their 20th birthdays, young men would be sorted into formal ibutho (plural amabutho) or regiments. They would build their ikhanda (often referred to as a 'homestead', as it was basically a stockade group of huts surrounding a corral for cattle), their gathering place when summoned for active service. Active service continued until a man married, a privilege only the king bestowed. The amabutho were recruited on the basis of age rather than regional or tribal origin. The reason for this was to enhance the centralised power of the Zulu king at the expense of clan and tribal leaders. They swore loyalty to the king of the Zulu nation.
Every ibutho was a thousand warriors’ strong and originally contained warriors from the same intanga, although this practice later changed as casualties suffered by the regiments made reinforcements necessary. Each ibutho had its own colour, which was used for shields, headdress and other ornaments. An impi - a force that contained several amabutho - was also accompanied by udibi, young boys who carried implements like cooking pots and sleeping mats and on occasion acted as scouts. Shaka insisted that troops wear no shoes—they could run faster and were not disabled by the loss of their sandals. Training for this was to stamp thorns into the ground with bare feet.