Shaka Zulu led a massive wave of military reform that catapulted the Zulu into being the most dominant native force in the region. Because of his many successful military reforms and his tactical brilliance some have even likened to to being "the black Napoleon".

Up to the time of his reforms, tribal warfare often focused on skirmish style confrontations with an emphasis on throwing spears. Shaka continued to train his forces to use throwing spears, but also put a new emphasis on hand to hand combat and melee with short stabbing spears.

He improved Zulu logistical ability, increased the speed that the Zulu army could move, and established a new regimental system that made chain of command more streamlined.

In addition to being a reformer, Shaka was also a great tactician and is personally credited for creating the "bull horn" formation which was extremely difficult for his opponents to counter.

This is a diagram of it: http://i.stack.imgur.com/4mIrw.png

Skirmishers and a large contingent of senior warriors in the front/middle (chest), two groups on either side of young, fast warriors who's job it was to flank around the enemy (horns), and in the back there would be a large reserve force (the loins) to patch up any holes the enemy was able to make once surrounded, and to pursue any enemies that escaped.