Bull horn formation
Once again, most Zulu successes rested on their mobility, ability to screen their forces and to close when their opponents were unfavourably deployed. Their major victory at the Battle of Isandlwana was the most prominent one, but they also forced back a British column at the Battle of Hlobane, by deploying fast-moving regiments over a wide area of rugged ravines and gullies, and attacking the British who were forced into a rapid disorderly fighting retreat, back to the town of Kambula.

Creator of a revolutionary warfare style: A number of historians argue that Shaka "changed the nature of warfare in Southern Africa" from "a ritualised exchange of taunts with minimal loss of life into a true method of subjugation by wholesale slaughter." Others dispute this characterization. A number of writers focus on Shaka's military innovations such as the iklwa – the Zulu thrusting spear, and the "buffalo horns" formation. This combination has been compared to the standardisation supposedly implemented by the reorganised Roman legions under Marius.

 Combined with Shaka's "buffalo horns" attack formation for surrounding and annihilating enemy forces, the Zulu combination of iklwa and shield—similar to the Roman legionaries' use of gladius and scutum—was devastating. By the time of Shaka's assassination in 1828, it had made the Zulu kingdom the greatest power in southern Africa and a force to be reckoned with, even against Britain's modern army in 1879.

Much controversy still surrounds the character, methods and activities of the Zulu king. From a military standpoint, historian John Keegan notes exaggerations and myths that surround Shaka, but nevertheless maintains:

 Fanciful commentators called him Shaka, the Black Napoleon, and allowing for different societies and customs, the comparison is apt. Shaka is without doubt the greatest commander to have come out of Africa.

As a borrower, not an innovator: Some scholars hold that popular depictions of Shaka as a suddenly appearing genius creating innovation are overstated, and that to the contrary, Shaka was a borrower and imitator of indigenous methods, customs and even ruler-lineages already in place. They also argue that Shaka's line was relatively short-lived and receives undue attention, compared to other, longer established lines and rulers in the region.

It seems much more likely that Shaka, seeking to build the power of a previously insignificant chiefdom, drew on an existing heritage of statecraft known to his immediate neighbors. J.H. Soga implied as much when he used genealogical evidence to argue that the Zulu were an upstart group inferior in dignity and distinction to established chiefdoms in their region, for example, the Hlubi, Ndwandwe, and Dlamini lines. Using different informants and genealogical charts, A.T. Bryant arrived at similar conclusions. The Zulu line – "a royal house of doubtful pedigree" – was very short in comparison to the Langene, Ndwandwe, Swazi, and Hlubi lines. Using his standard formula of eighteen years per reign, Bryant calculated that the Swazi, Ndwandwe, and Hlubi lines could be traced back to the beginning of the fifteenth century, while the eponymous chief Zulu had died at the beginning of the eighteenth century.
Shaka's triumphs did not succeed in obliterating or diminishing the memories of his better-born rivals. The hypothesis that several states of a new kind arose about the same time does not take account of the contrast between the short line of Shaka and the long pedigrees of his most important opponents – especially the coalition grouped around his deadly enemy Zwide (d. 1822). The founders of the states which Omer-Cooper called "Zulu-type states," including the Ndebele, the Gasa, the Ngoni, and the Swazi had all been closely associated with Zwide. Instead of hypothesizing that they all chose to imitate Shaka, it is easier to imagine that he modeled his state on theirs. And as they stemmed from ancient families it is entirely possible that states of that type existed in a more remote past. Soga and Bryant related each of them to a larger grouping they called Mho.

Scholarship: 

Biographical sources: Scholarship in recent years has revised views of the sources on Shaka's reign. The earliest are two eyewitness accounts written by European adventurer-traders who met Shaka during the last four years of his reign. Nathaniel Isaacs published his Travels and Adventures in Eastern Africa in 1836, creating a picture of Shaka as a degenerate and pathological monster, which survives in modified forms to this day. Isaacs was aided in this by Henry Francis Fynn, whose diary (actually a rewritten collage of various papers) was edited by James Stuart only in 1950. Their accounts may be balanced by the rich resource of oral histories collected around 1900 by the same James Stuart, now published in six volumes as The James Stuart Archive. Stuart's early 20th century work was continued by D. McK. Malcolm in 1950. These and other sources such as A.T. Bryant gives us a more Zulu-centred picture. Most popular accounts are based on E.A. Ritter's novel Shaka Zulu (1955), a potboiling romance that was re-edited into something more closely resembling a history. John Wright (history professor at University of KwaZulu-Natal, Pietermaritzburg), Julian Cobbing and Dan Wylie (Rhodes University, Grahamstown) are among a number of writers who have modified these stories.
Various modern historians writing on Shaka and the Zulu point to the uncertain nature of Fynn and Isaac's accounts of Shaka's reign. A general reference work in the field is Donald Morris's "The Washing of The Spears", which notes that the sources, as a whole, for this historical era are not the best. Morris references a large number of sources, including Stuart, and A. T. Bryant's "Olden Times in Zululand and Natal", which is based on four decades of interviews of tribal sources. After sifting through these sources and noting their strengths and weaknesses, Morris generally credits Shaka with a large number of military and social innovations. This is the general consensus in the field.
A 1998 study by historian Carolyn Hamilton summarizes much of the scholarship on Shaka towards the dawn of the 21st century in areas ranging from ideology, politics and culture, to the use of his name and image in a popular South African theme park, Shakaland. It argues that in many ways, the image of Shaka has been "invented" in the modern era according to whatever agenda persons hold. This "imagining of Shaka" it is held, should be balanced by a sober view of the historical record, and allow greater scope for the contributions of indigenous African discourse.
Military historians of the Zulu War describe Zulu fighting methods and tactics, including authors Ian Knight and Robert Edgerton. General histories of Southern Africa include Noel Mostert's "Frontiers" and a detailed account of the results from the Zulu expansion, J.D. Omer-Cooper's "The Zulu Aftermath", which advances the traditional Mfecane/Difaqane theory.

The Mfecane: 

History and legacy: The increased military efficiency led to more and more clans being incorporated into Shaka's Zulu empire, while other tribes moved away to be out of range of Shaka's impis. The ripple effect caused by these mass migrations would become known (though only in the twentieth century) as the Mfecane/Difaqane (annihilation).
Shaka's army set out on a massive programme of expansion, killing or enslaving those who resisted in the territories he conquered. His impis (warrior regiments) were rigorously disciplined: failure in battle meant death.
At the time of his death, Shaka ruled over 250,000 people and could muster more than 50,000 warriors. His 10-year-long kingship resulted in a massive number of deaths, mostly due to the disruptions the Zulu caused in neighbouring tribes, although the exact death toll is a matter of scholarly dispute. Further unquantifiable deaths occurred during mass tribal migrations to escape his armies.
The Mfecane produced Mzilikazi of the Khumalo, a general of Shaka's. He fled Shaka's employ, and in turn conquered an empire in Zimbabwe, after clashing with European groups like the Boers. The settling of Mzilikazi's people, the AmaNdebele or Matabele, in the south of Zimbabwe with the concomitant driving of the Mashona into the north caused a tribal conflict that still resonates today. Other notable figures to arise from the Mfecane/Difaqane include Soshangane, who expanded from the Zulu area into what is now Mozambique, and Zwangendaba.

Disruptions of the Mfecane/Difaqane: The theory of the Mfecane holds that the aggressive expansion of Shaka's armies caused a brutal chain reaction across the southern areas of the continent, as dispossessed tribe after tribe turned on their neighbours in a deadly cycle of fight and conquest. Some scholars contend that this theory must be treated with caution as it generally neglects several other factors such as the impact of European encroachment, slave trading and expansion in that area of Southern Africa around the same time.