During the 14th century, the King of Tonga delegated much of his temporal power to a brother while retaining the spiritual authority. Sometime later, this process was repeated by the second royal line, thus resulting in three distinct lines: the Tu'i Tonga with spiritual authority, which is believed to have extended over much of Polynesia; the Tu'i Ha'atakalaua; and the Tu'i Kanokupolu. The latter two had temporal authority for carrying out much of the day-to-day administration of the kingdom.

Dutch navigators in 1616 were the first Europeans to sight the Tongan archipelago. The main island of Tongatapu was first visited by the Dutch explorer Abel Tasman in 1643. Continual contact with Europeans, however, did not begin until more than 125 years later. Captain James Cook visited the islands in 1773 and 1777 and gave the archipelago the name "the Friendly Islands" because of the gentle nature of the people he encountered. He, of course, was never aware of the acrimonious debate that raged among contending nobles over who should have the honor of attacking Cook's tiny fleet and killing its sailors. In 1789, the famous mutiny on the British ship, Bounty, took place in the waters between the Ha'apai and Nomuka island groups.

Shortly after Captain Cook's last visit, warfare broke out in the islands as the three lines of kings contended for dominance. At about the same time, young Tongan nobles serving as mercenaries took Tongan culture to Fiji's most eastern island group, the Laus. The first missionaries, attached to the London Missionary Society, arrived in Tonga in 1747. A second missionary group followed in 1822, led by Walter Lawry of the Wesleyan Missionary Society. They converted Taufa'ahau, one of the claimants to the Tu'i Kanokupolu line, and Christianity began to spread throughout the islands.

At the time of his conversion, Taufa'ahau took the name of Siaosi (George) and his consort assumed the name Salote (Charlotte) in honor of King George III and Queen Charlotte of England. In the following years, he united all of the Tongan islands for the first time in recorded history. In 1845, he was formally proclaimed King George Tupou I, and the present dynasty was founded. He established a constitution and a parliamentary government based, in some respects, on the British model. In 1862, he abolished the existing system of semi-serfdom and established an entirely alien system of land tenure. Under this system every male Tongan, upon reaching the age of 16, was entitled to rent -- for life and at a nominal fee -- a plot of bushland (called "api") of 8.25 acres, plus a village allotment of about three-eights of an acre for his home.

Tonga concluded a treaty of friendship and protection with the United Kingdom in 1900 and came under British protection. It retained its independence and autonomy, while the United Kingdom agreed to handle its foreign affairs and protect it from external attack.

During World War II, in close collaboration with New Zealand, Tonga formed a local defense force of about 2,000 troops that saw action in the Solomon Islands. In addition, New Zealand and U.S. troops were stationed on Tongatapu, which became a staging point for shipping.

A new treaty of friendship and protection with the United Kingdom, signed in 1958 and ratified in May 1959, provided for a British Commissioner and consul in Tonga who were responsible to the Governor of Fiji in his capacity as British Chief Commissioner for Tonga. In mid-1965 the British Commissioner and consul became directly responsible to the U.K. Secretary of State for Colonial Affairs. Tonga became fully independent on June 4, 1970, an event officially designated by the King as Tonga's "reentry into the community of nations."