From 1868 to 1871, he commanded Ngāti Porou war parties in the pursuit of Te Kooti, a rebel Māori leader whose religious movement, Ringatū, threatened the security of the East Cape region.

During the conflict he played a key role in the capture of Te Kooti's pā (hill fort) at Ngatapa, for which he was awarded the New Zealand Cross and was made a major in the Volunteer Force.

However, in later years when he rose to prominence he worked closely with Donald McLean who, having a broad Scottish accent, habitually pronounced his name as "Ropata" and it became the name by which he is generally known.

[1] Ngāti Porou had become divided following the arrival on the East Cape that year of the leaders of the Pai Mārire religious movement.

On 5 June, he was among a number of Te Aowera attending celebrations for the establishment of a church at Popoti, when they were advised that some Hauhau had arrived in the Waiapu Valley.

[1][5] When the Hauhau arrived in Waiapu Valley, Mōkena Kōhere, a senior rangatira of Ngāti Porou, had appealed to Donald McLean, the superintendent for the Hawke's Bay Province, for assistance.

[7] He was also regarded as ruthless: according to an account written in 1879 by Walter Gudgeon, at one point Ropata found some men from his own hapū, Te Aowera, among a group of Hauhau prisoners and he personally shot each one.

Monty Soutar, a Ngāti Porou historian, disputes this, writing in 2000 that no evidence in contemporary records could be found to support this action occurred.

Ropata gathered a Ngāti Porou war party of 300 warriors and joined the militia in what amounted to a seven-day siege on Waerenga-a-hika that commenced in mid-November.

When the force was ambushed on 12 January and its lead elements began to fall back, Ropata helped restore morale, moving forward and setting fire to the undergrowth which obscured the vision of the Hauhau.

[13] After two years, the prisoners had become frustrated at their treatment, having been held without trial, and Te Kooti led them in surprising their guards and seizing a vessel to sail back to New Zealand.

[16] Te Kooti, after mounting a raid on 10 November that saw a number of Māori and European settlers and farmers murdered,[17] retreated to a strong defensive pā at Ngatapa.

[20] The first assault on 4 December, led by Ropata, Hōtene Porourangi, another rangatira of Ngāti Porou, and Lieutenants Mair and Preece of the Armed Constabulary, was unsuccessful.

[24] Whitmore now had nearly 700 men, including 370 Ngāti Porou and 60 warriors of Te Arawa iwi, from the Bay of Plenty, under his command for an attack on Ngatapa.

[28] Whitmore sought Ropata's assistance for a campaign against Titokowaru, another rebel chief, in the Wanganui area, on the opposite coast of the North Island.

Ropata declined to join; he, along with Donald McLean and Karaitiana Takamoana, the Ngāti Kahungunu rangatira, felt that Te Kooti remained a threat to the East Cape region and did not want to see the area and his people defenceless.

[30] The Urewera country, to the west of East Cape, was rugged, mountainous terrain, and thickly forested, the home of the Ngāi Tūhoe iwi.

Ngāti Porou warriors were slow to become involved in Whitmore's invasion of the Urewera country, only joining an expedition at Lake Waikaremoana in late May and that was withdrawn the following month after Te Kooti moved to the Taupo plains.

This was at the instigation of McLean, now the Minister of Defence, who had noted the success achieved by the kūpapa in the hunt for Te Kooti compared to the Armed Constabulary.

[35] Only one pākeha was allowed to accompany each of the Māori war parties; Ropata asked for and got Captain Thomas Porter, an officer of the Voluntary Cavalry in Poverty Bay.

[38] In his later writings, Porter commented favourably on Ropata's leadership and the resulting discipline and loyalty he instilled in his Ngāti Porou during the march to Maungapohatu, a key site for the Tūhoe.

McLean was pleased with the result and rewarded Ngāti Porou by announcing the withdrawal of the Government's claim to disputed land on the East Cape.

This prompted Ropata to raise another contingent of Ngāti Porou to pursue Te Kooti; Crosby notes his motivation was likely to ensure that McLean kept his word.

[50][51] Porter and Ropata, now recovered from his illness, met up at Maungapohatu, and then moved onto Ruatahuna, where they were advised that Kereopa Te Rau, who was one of the Hauhau involved in the murder of Völkner in 1865, was living a few hours away.

Following this, Tūhoe made peace with the Government, and Ropata withdrew his party, ending the Ngāti Porou campaigns in the Urewera country.

Ropata and Porter, still working together, were appointed by the then Prime Minister, Harry Atkinson, to make sure Te Kooti did not enter the East Cape or Urewera country.

Ngāti Porou were mobilised and arrived on the scene just as Te Kooti was arrested by a police inspector, in time to prevent his followers from making a violent issue of it.

He was buried with full military honours nearly two weeks later at an urupā (burial ground) on Puputa, a rocky outcrop behind the Porourangi marae at Waiōmatatini.

According to Crosby, Ropata should be more correctly characterised as being loyal to his iwi and the honouring of the Treaty of Waitangi, which guaranteed the security of Ngāti Porou lands.

He took a pragmatic approach to collaboration with the Government to ensure his iwi's land was not confiscated given that at least some Ngāti Porou became Hauhau during the East Cape War.