The Tauranga campaign was a six-month-long armed conflict in New Zealand's Bay of Plenty in early 1864, and part of the New Zealand Wars that were fought over issues of land ownership and sovereignty. The campaign was a sequel to the invasion of Waikato, which aimed to crush the Māori King (Kingitanga) Movement that was viewed by the colonial government as a challenge to the supremacy of the British monarchy.
British forces suffered a humiliating defeat in the Battle of Gate Pā on 29 April 1864, with 31 killed and 80 wounded despite outnumbering their Māori foe, but saved face seven weeks later by routing their enemy at the Battle of Te Ranga, in which more than 100 Māori were killed or fatally wounded, including their commander, Rawiri Puhirake.
Background
In late January 1864 British commander General Duncan Cameron—at the time still facing the intimidating Paterangi line of Māori defences in the Waikato campaign—despatched by sea an expedition to occupy Tauranga, through which he believed his enemy were transporting men and supplies from the East Coast. The local Ngāi Te Rangi Māori were hostile to the government, a major gunpowder store was known to be inland of Tauranga and the district was an important source of food for Māori fighting British forces in the Waikato. While Colonel Henry Greer was landed with his force at Te Papa, where they built two redoubts, Captain Robert Jenkins, commander of HMS Miranda, was ordered to blockade the harbour to prevent the arrival of more Māori reinforcements.
thumb|left|150px|Lieutenant-General [[Duncan Alexander Cameron|Duncan Cameron, Commander-in-Chief of British forces in New Zealand, 1863–1865.]]
Though Cameron's strategy gained the enthusiastic support of Premier Frederick Whitaker and his cabinet, who were keen to use the 1863 confiscations legislation to open fresh territory for European settlement, Governor George Grey was opposed, fearing it would raise rebellion in more Māori tribes, including those that had thus far refrained from supporting the Kingitanga movement. Grey withdrew his initial assent for Whitaker's orders to take an aggressive stance and instead directed the Tauranga expedition's commander, Brigadier George Carey, to remain strictly on the defensive, apart from intercepting armed bands en route to the Waikato.
Meanwhile, fighting had already broken out nearby. A large contingent of East Coast Māori, possibly as many as 700 warriors, were making their way towards the conflict at Waikato. Their route took them through the territory of another tribe which saw themselves as allies of the Pākehā, the Arawa tribe based around Rotorua. Forewarned of this, the Arawa chiefs called back their tribesmen, many of whom were working in Auckland or further north. Pausing in Tauranga to borrow guns from the British, they hastened onward to Rotorua. Four hundred warriors of the tribe were mobilised and they met and held the East Coast Māori on 7 April in a two-day battle on the shores of Lake Rotoiti. On 27 April fighting broke out again on the coast, with Māori loyal to the Crown supported by the 43rd Regiment and British corvettes firing on Kingite Māori as they were pursued through the sand dunes.
Battle of Gate Pā
thumb|250px|right|Plan of the attack on Gate Pā
thumb|right|250px|Gate Pā, based on a sketch by Lieutenant [[Horatio Gordon Robley.]]
Still hoping to provoke an attack, the 250 Ngāi Te Rangi fighters at Pukehinahina enlarged the existing trench and banks and transformed the pā into a system of two redoubts, including a honeycomb of rua, or anti-artillery bunkers. Ngāi Te Rangi garrisoned the main redoubt, and about 30 members of the Ngāti Koheriki hapu and another 10 men from Piri-Rikau and other hapu manned the smaller redoubt. With timber scarce in surrounding swampland, palisading was frail, but the location of the redoubt on a hilltop, and the total span of the palisading gave their enemy the impression of greater strength than it actually possessed. In all, the total garrison of Gate Pā was about 230 men.
On 5 April, Cameron abandoned hope of pursuing Ngāti Hauā leader and prominent Kingite Wiremu Tamihana after his foe evacuated the besieged Te Tiki o te Ihingarangi pā near Lake Karapiro. Cameron switched his attention to Tauranga, arriving there on 21 April in and established his headquarters at Tauranga. In addition to the reinforcements on Esk, more from Auckland arrived on . Within days Cameron decided he had sufficient forces to finally march against Gate Pā.
On the afternoon of 28 April, Cameron launched an hour-long attack on the front of Gate Pā with four batteries of artillery placed at a range of between 350 and 800 metres. The battery—the heaviest used in the wars of 1863–1864—included a 110-pounder Armstrong gun, two 40-pounder and two six-pounder Armstrongs, two 24-pounder howitzers, two eight-inch mortars, and six Coehorn mortars.
Late in the night Greer moved his 700 men from the 68th Regiment across swamps to the east of Gate Pā under cover of darkness and rain to take up a position to the rear of the redoubt to cut off a Māori retreat. Those forces were joined by a detachment of the Naval Brigade from the warships Esk, Falcon and . By daybreak on 29 April Cameron had a total of about 1,650 men surrounding the pā: 700 of the 68th Regiment, 420 from the Naval Brigade, 300 of the 43rd Regiment, 50 Royal Artillery, and another 180 members of the 12th, 14th, 40th and 65th Regiments. killing about 15 of the defenders.
thumb|left|The attack on the pā (from a British book)
At about 4pm, with no sign of life in the pā, Cameron ordered an assault by 300 men—a combined force of Naval Brigade under Commander Hay and the 43rd Regiment, led by Lieutenant-Colonel H.G. Booth—who ran in four abreast with fixed bayonets. Another 300 men followed at a distance as a reserve. Some in the initial British assault force were shot as they entered the main pā, and inside the redoubt more fell as they engaged in hand-to-hand combat with Māori armed with shotguns and mere (short clubs). A lull of about five minutes occurred, during which time Captain G.R. Greaves, who was with the leading files of the assault party, left the pā and reported to Cameron that the redoubt had been captured and that British casualties were light.|group=Note Belich claims that by providing only a feeble defence from the garrison during the storming of the pā and keeping his garrison hidden, Rawiri Puhirake employed a "remarkable tactical ploy ... brilliantly implemented as well as brilliantly conceived" to lure the British into a deadly trap.