Hongi Hika had his early training in warfare in a series of border squabbles between Ngapuhi and the people of southern Hokianga. He was later one of the chiefs who suffered a sharp defeat at the hands of the Ngati Whatua tribe at Moremo-nui, between Hokianga and Kaipara, in 1807. On this occasion the Ngapuhi guns were helpless against a surprise attack by Ngati Whatua armed only with traditional Maori weapons. Eighteen years later this defeat was amply avenged at the battle of Te Ika-a-ranganui.
In the meantime, however, Hongi in 1818 embarked on a naval expedition with a combined force of 800 men from Ngapuhi and from Ngati Maru of the Hauraki district. The expedition, which was primarily bent on obtaining revenge for some Ngapuhi women murdered at East Cape some time before, attacked various tribes at Maketu, Maraenui (near Opotiki), and Hicks Bay, where the Ngati Maru leader Te Haupa was killed. Hongi returned to the Bay of Islands in January 1819 with a large number of prisoners, said to be about 2,000, and with many preserved heads of slain enemies.
In March 1820 Hongi departed for England to procure supplies of firearms. While in England he was made much of and was given many presents, which he later converted into cash to buy guns and powder. He returned home in July 1821 and in less than two months he embarked upon a campaign of death and destruction which lasted almost until his death. In September Hongi assembled a vast fleet of war canoes and left the Bay of Islands with 2,000–3,000 men, 1,000 of whom were armed with muskets. Their object was to obtain vengeance for losses inflicted on Hongi's people by the Ngati Maru of the Thames district. After attacking a settlement at Te Waiti about 20 miles north of Auckland, the Ngapuhi army proceeded to the Tamaki area, where they laid siege to Mokoia and Mau-inaina, the fortified pa of the Ngati Pao tribe. After a protracted siege the Ngapuhi, led by Hongi, Te Morenga, Taki, and many other chiefs, finally carried the pa. It is said that 1,000 Ngati Paoa were slain during the fighting and after the battle was over. Many escaped, however, by swimming the Tamaki River.
Hongi then led his army to Te Totara, a strong position of the Ngati Maru tribe south of Parawai, near the present town of Thames. Many of the local tribe were away from home on the expedition to the southern parts of the North Island, known as “Amio whenua”. At the same time there were in Te Totara various visitors from Waikato, Te Arawa, Ngati Raukawa, and other tribes. Despite his superiority in arms Hongi was unable to take the pa by assault. He therefore pretended to make peace and made a feint withdrawal. During the night he returned to the unguarded pa and captured it, killing many of the inmates.
As a result of the slaying of some Waikato children at Mau-inaina, a party of Waikato warriors went to Whangarei at the end of 1821 or early in 1822 and inflicted casualties on the local Ngapuhi. This and other incidents led to a retaliatory attack on the Waikato tribe by Hongi Hika. Hongi left the Bay of Islands in February 1822 with 3,000 men. They carried their canoes across the portage at Otahuhu and then crossed another portage at Waiuku to the headwaters of the Awaroa Stream, a tributary of the Waikato. Progress was slow because of the many trees which had been felled across the stream by subtribes of Waikato.
In the meantime the Waikato were gathering at Matakitaki, a large pa at the junction of the Mangapiko Stream and the Waipa River. Eventually there were 10,000 men, women, and children in the pa, which was under the command of Potatau Te Wherowhero. Few of the Waikato had encountered firearms before. Ngapuhi besieged the pa in May. After a period of inaction they assaulted the pa under cover of heavy musket fire, which created panic amongst the Waikato. In a short time Ngapuhi captured the pa and then began a hunt for fugitives throughout the Waikato. Te Wherowhero escaped and in numerous running engagements his remaining warriors inflicted some losses on Ngapuhi. Hongi finally withdrew after inflicting grievous casualties and arrived back in the Bay of Islands in July 1822. In the following year Rewa, a Ngapuhi chief, returned to Waikato and made peace with Te Wherowhero.
In 1823 Hongi assembled another army and set out to avenge the deaths of some of his tribesmen at the hands of the Arawa people of Rotorua. On arriving in the district Hongi found that the Arawa had withdrawn to Mokoia Island in Lake Rotorua and that all of their canoes had been gathered there. Hongi's determination, however, was equal to this obstacle and he arranged for his army to bring canoes from the Bay of Plenty. They paddled and dragged the canoes up the Pongakawa River from near Maketu to Lake Rotoehu, then carried them overland to Lake Rotoiti by what is now called Hongi's Track. As there were no further obstacles Hongi was then able to assault the fortress on Mokoia. With his great superiority in firearms he had no great difficulty in overcoming the Arawa warriors. After feasting on the slain and pursuing scattered Arawa parties throughout the district the Ngapuhi went back to the Bay of Plenty and then on to Waihi, where they camped for a few days and completed a peacemaking ceremony with the Arawa.
Two of Hongi's leaders, Pomare and Te Wera, left the main party at Waihi and set off on an expedition to southern parts. Hongi and the main body returned to the Bay of Islands.
In 1825 Hongi took up the traditional feud of Ngapuhi with their neighbours, Ngati Whatua, who had by this time occupied most of the Kaipara district and the area down to Tamaki. The defeat of Ngapuhi at the battle of Moremu-nui in 1807 had not been adequately avenged. Hongi now attended to this thoroughly in defeating Ngati Whatua at the battle of Te Ika-a-ranga-nui, a place situated about a mile up the Waimako Stream from its junction with the Kaiwaka. Many of the survivors fled south to the Waikato area.
Hongi returned home for a few months and then set out to follow the Ngati Whatua fugitives. He sailed down the east coast, thence across the portages at Otahuhu and Waiuku. Paddling up the Waikato, Waipa, and Mangapiko Rivers, the Ngapuhi came to Noho-awatea, where the Ngati Whatua had taken refuge with the Ngati Paoa, themselves fugitives from the battle of Mau-inaina four years earlier.
By one of those strange alliances not uncommon in Maori history, the Ngapuhi were joined by Ngati Haua, a Waikato tribe from the Matamata area. On this occasion they asked their relations, the Ngati Paoa, to leave the pa, and Te Rauroha, the Ngati Paoa leader, withdrew with his followers, leaving Ngati Whatua to their fate. The pa was taken and many of the Ngati Whatua were slain.
This was Hongi's last expedition of any note to the south. In January 1827 he was wounded in a fight with the tribes of Whangaroa and Hokianga which took place at Hunuhunua on the banks of the Mangamuka Stream. Hongi was carried home and died in March 1828.