The Zulus avoided the dispersal of their main fighting force and concealed the advance and location of this force until they were within a few hours' striking distance of the British.
When the location of the main Zulu Impi was discovered by British scouts, the Zulus immediately advanced and attacked, achieving tactical surprise.
The British, although they now had some warning of a Zulu advance, were unable to concentrate their central column.
It also left little time and gave scant information for Pulleine to organise the defence.
The Zulus had outmanoeuvred Chelmsford and their victory at Isandlwana was complete and forced the main British force to retreat out of Zululand until a far larger British army could be shipped to South Africa for a second invasion.

Recent historians, notably Lock and Quantrill in Zulu Victory, argue that from the Zulu perspective the theatre of operations included the diversions around Magogo Hills and Mangeni Falls and that these diversions, which drew more than half of Chelmsford's forces away from Isandlwana, were deliberate.
Also, the main Zulu force was not unexpectedly discovered in their encampment but was fully deployed and ready to advance on the British camp.
These historians' view of the expanded battlefield considers Chelmsford to have been the overall commander of the British forces and that responsibility for the defeat lies firmly with him.

Debate persists as to how and why the British lost the battle.
Many arguments focus on possible local tactical occurrences, as opposed to the strategic lapses and failings in grand tactics on the part of high command under Bartle Frere and Chelmsford.
Still, the latter comes under scrutiny for mistakes that may have led directly to the British defeat.
The initial view, reported by Horace Smith-Dorrien, was that the British had difficulty unpacking their ammunition boxes fast enough.
 The box lids were screwed down, the screws were rusty and difficult to remove, there were too few screwdrivers, "standing orders" insisted that until a box was empty, no other boxes were to be opened, and  the quartermasters were reluctant to distribute ammunition to units other than their own.
Well-equipped and well-trained British soldiers could fire 10–12 rounds a minute.
The lack of ammunition caused a lull in the defence and, in subsequent engagements with the Zulus, ammunition boxes were unscrewed in advance for rapid distribution.
Numerous first hand accounts indicate ammunition was available and being supplied, including Smith-Dorrien's earliest in a letter to his father.

Donald Morris in The Washing of the Spears argues that the men, fighting too far from the camp, ran out of ammunition, starting first with Durnford's men who were holding the right flank and who had been in action longer, which precipitated a slowdown in the rate of fire against the Zulus.
This argument suggests that the ammunition was too far from the firing line and that the seventy rounds each man took to the firing line were not sufficient.
A different view, supported with evidence from the battlefield, such as Ian Knight and Lt.
Colonel Snook's works, (the latter having written How Can Man Die Better?),
suggests that, although Durnford's men probably did run out of ammunition, the majority of men in the firing line did not.
The discovery of the British line so far out from the camp has led Ian Knight to conclude that the British were defending too large a perimeter.

The official interrogation by Horse Guards under the direction of the Duke of Cambridge, the Field Marshal Commanding in Chief, in August 1879, concluded that the primary cause of the defeat was the "under estimate formed of the offensive fighting power of the Zulu army", additionally the investigation questions Chelmsford as to why the camp was not laagered and why there was a failure to reconnoitre and discover the nearby Zulu army.
Colenso calls Chelmsford's neglecting to follow his own "Regulations for Field Forces in South Africa", which required that a defensible camp be established at every halt, fatal.

Numerous
The Zulus avoided the dispersal of their main fighting force and concealed the advance and location of this force until they were within a few hours' striking distance of the British. When the location of the main Zulu Impi was discovered by British scouts, the Zulus immediately advanced and attacked, achieving tactical surprise. The British, although they now had some warning of a Zulu advance, were unable to concentrate their central column. It also left little time and gave scant information for Pulleine to organise the defence. The Zulus had outmanoeuvred Chelmsford and their victory at Isandlwana was complete and forced the main British force to retreat out of Zululand until a far larger British army could be shipped to South Africa for a second invasion.
Recent historians, notably Lock and Quantrill in Zulu Victory, argue that from the Zulu perspective the theatre of operations included the diversions around Magogo Hills and Mangeni Falls and that these diversions, which drew more than half of Chelmsford's forces away from Isandlwana, were deliberate. Also, the main Zulu force was not unexpectedly discovered in their encampment but was fully deployed and ready to advance on the British camp. These historians' view of the expanded battlefield considers Chelmsford to have been the overall commander of the British forces and that responsibility for the defeat lies firmly with him.
Debate persists as to how and why the British lost the battle. Many arguments focus on possible local tactical occurrences, as opposed to the strategic lapses and failings in grand tactics on the part of high command under Bartle Frere and Chelmsford. Still, the latter comes under scrutiny for mistakes that may have led directly to the British defeat. The initial view, reported by Horace Smith-Dorrien, was that the British had difficulty unpacking their ammunition boxes fast enough.  The box lids were screwed down, the screws were rusty and difficult to remove, there were too few screwdrivers, "standing orders" insisted that until a box was empty, no other boxes were to be opened, and  the quartermasters were reluctant to distribute ammunition to units other than their own. Well-equipped and well-trained British soldiers could fire 10–12 rounds a minute. The lack of ammunition caused a lull in the defence and, in subsequent engagements with the Zulus, ammunition boxes were unscrewed in advance for rapid distribution. Numerous first hand accounts indicate ammunition was available and being supplied, including Smith-Dorrien's earliest in a letter to his father.
Donald Morris in The Washing of the Spears argues that the men, fighting too far from the camp, ran out of ammunition, starting first with Durnford's men who were holding the right flank and who had been in action longer, which precipitated a slowdown in the rate of fire against the Zulus. This argument suggests that the ammunition was too far from the firing line and that the seventy rounds each man took to the firing line were not sufficient. A different view, supported with evidence from the battlefield, such as Ian Knight and Lt. Colonel Snook's works, (the latter having written How Can Man Die Better?), suggests that, although Durnford's men probably did run out of ammunition, the majority of men in the firing line did not. The discovery of the British line so far out from the camp has led Ian Knight to conclude that the British were defending too large a perimeter.
The official interrogation by Horse Guards under the direction of the Duke of Cambridge, the Field Marshal Commanding in Chief, in August 1879, concluded that the primary cause of the defeat was the "under estimate formed of the offensive fighting power of the Zulu army", additionally the investigation questions Chelmsford as to why the camp was not laagered and why there was a failure to reconnoitre and discover the nearby Zulu army. Colenso calls Chelmsford's neglecting to follow his own "Regulations for Field Forces in South Africa", which required that a defensible camp be established at every halt, fatal.
Numerous 
Battle of Isandlwana