Major conflicts within the campaign included the cavalry and artillery attack on Te Tarata pā near Ōpōtiki in October 1865 in which about 35 Māori were killed and the seven-day siege of Waerenga-a-Hika in November 1865.

In 2013 the Crown paid $23 million in financial redress and expressed "profound regret" over the "unjust attacks" in Hawke's Bay in 1866 and apologised for subsequent land confiscations.

In many parts of the North Island, the resultant resentment and anger found expression in the more radical, nationalistic elements of Pai Mārire, which sought to drive European settlers from the land.

Pai Mārire had begun in Taranaki as a peaceful religion, a combination of Christianity and traditional Māori beliefs, but by 1865 had developed a reputation as a violent and vehemently anti-Pākehā (European) movement.

The arrival and rapid spread of Pai Mārire in the East Cape destabilised the region, dividing Māori communities and also causing great alarm among New Zealand settlers despite the fact the area was almost devoid of European settlement.

The government responded with several ad hoc measures, including supplying arms to "loyal" factions, organising a force of Arawa tribesmen under European leaders, and a series of small expeditions of volunteer settlers from Hawke's Bay.

[4] A poorly-armed Māori party led by chiefs including Ropata Wahawaha mounted an unsuccessful raid on Pai Mārire adherents at Mangaone, near Pukemaire, on 10 June 1865.

[5] After several more small engagements in the Waiapu Valley a delegation of east coast chiefs led by Mokena Kohere appealed to Donald McLean, the new Provincial Superintendent of Hawke's Bay, for arms and reinforcements to subdue the uprising.

HMS Eclipse landed the troops at Hicks Bay and at the mouth of the Waiapu River on 5 July 1865 in a bid to capture Kereopa and Patara, shelling their Hauhau enemy the next day.

[6] When a trading cutter following the troops anchored off Whakatane on 22 July to allow surveyor and government interpreter James Fulloon to go ashore to investigate the local mood, it was boarded by Pai Mārire converts at the orders of Taranaki prophet Horomona.

[2] Without informing the British commander in New Zealand, General Duncan Cameron, Governor George Grey delegated large powers to McLean to use friendly Māori and local volunteers to put down disturbances and punish Volkner's killers.

On 18 August at a pā between Tokomaru and Tolaga Bay a heavily outnumbered force of 36 men under Henare Potae was reinforced by another 90 under Ropata in a sharp and bloody engagement.

[5] On 2 September 1865 the government declared martial law on the east coast and announced a new expedition against Volkner's killers, threatening confiscation of land in the area if they were not handed over.

[9] The expeditionary force remained in Ōpōtiki for several weeks, converting Volkner's church into a redoubt and engaging in occasional clashes with Māori, who established the entrenched and palisaded Te Puia pā about 8 km inland.

The East Coast Expedition, now under the control of Major Charles Stapp, moved its base to the captured Te Puia and the Whakatohea fell back to new strongholds in the Waioeka Gorge.

Early on 20 October the force reached Koingo, a small village on the Waimana River and set up an ambush of a track; Kereopa was targeted but escaped, although five others accompanying him were shot.

They opened a flying sap and managed to destroy part of the frail palisade but abandoned attempts to storm the pa when rain rendered their weapons ineffectual.

In October Ropata and Lieutenant Reginald Biggs led a small force, including Forest Rangers, to the new Pai Marire base, scaling nearby cliffs to launch an effective sniping operation, killing 20 occupants and wounding others.

[10][5] In late October 1865 McLean began planning an expedition against the Waerenga-a-Hika pā—a Pai Mārire community about 11 km from the European settlement at Turanga (modern-day Gisborne)—where several hundred men, as well as women and children, had sought refuge from the east coast wars.

[11] The government force, comprising up to 200 Europeans and 300 Māori, moved on Waerenga-a-Hika on 16 November and took up positions on three sides of the pā, which had a swampy lagoon to the rear, and began a seven-day siege.

A squad of 30 Military Settlers began a sap towards the north face of the stockade and neared it before coming under attack from Pai Mārire reinforcements from one of the other villages on 18 November.

The following day, a Sunday, Pai Mārire fighters were driven off after advancing on the government soldiers in three groups in an action that left between 34 and 60 Māori dead, although there are conflicting accounts of the engagement.

[11][14] In Fraser's account of the same events, the armed Pai Mārire force advanced from the pā under a white flag of truce, which Fraser viewed as a ruse, "as no flag of truce should be respected carried by such a large body of armed men, and I ordered them to be fired on before they could come up to us ... the enemy were totally defeated, with the loss of 34 killed, and at least that number wounded, their men falling in all directions as they attempted to regain their pa".

[15] On 22 November, after a week of constant rifle fire, Fraser turned to artillery to end the siege, loading shrapnel-filled salmon tins into a six-pounder cannon from the Sturt to create makeshift canister shot.

After two rounds were fired into the pā the demoralised garrison hoisted a white flag and 400 occupants surrendered; they were taken to Gisborne to be either released or shipped to the Chatham Islands for imprisonment.

[16] Among the kūpapa at Waerenga-a-Hika was future Māori guerrilla leader Te Kooti, who was taken prisoner (but later released) on suspicion of treachery after allegations that he was collaborating with the enemy and firing blanks.

[11][16] Despite a general surrender at the fall of Waerenga-a-Hika on 22 November, Pai Mārire reinforcements from Turanganui, who had arrived with chiefs Anaru Matete and Te Waru Tamatea during the siege to battle Fraser's forces, were able to escape.

[12] In early January McLean sent a messenger to Waikaremoana chiefs demanding that they abandon "Hauhauism", deliver up their arms and hand themselves in to swear the oath of allegiance if they wished to spare their lives.

Two days later they captured a near-empty Pai Mārire pā about 20 km up the Waikaretaheke River, but soon after realised they had been lured into a trap when they were ambushed from hidden rifle pits in the ridges overlooking the track.

In a firefight that lasted about an hour, Whitmore's force killed about 31 Ngāti Hineuru, wounded 28 (of whom many later died in hospital) and captured 44 others who attempted to flee, thus accounting for almost all the occupants.