In 1916 a few of the islands in the Line Island chain (in Kiribati's far east) joined this union and later most of the rest of the Line Islands joined as well. All of these islands were eventually incorporated into the British colony called the British Western Pacific Territories. At this time the rest of the Line Islands, as well as the Phoenix Islands fell under the Jurisdiction of the United States.
Throughout this period of British rule foreigners settled the islands, but these islands were never a focus of British colonization and never became a significant immigration destination for the British or other foreign nationals. Because of this, little changed in the culture of the people of Kiribati during these years. The two most significant and longest lasting changes during this time came in the form of technology, such as new communication and transportation, and the introduction of Christianity.
Missionaries from the United Kingdom and other countries arrived to the islands to spread Christianity and they did so very successfully. This was likely the most important change to the people, their lifestyle, and their culture instigated by the British and other foreigners on the islands, including the Americans in the Phoenix Islands and Line Islands.
The primary reason few other cultural changes took place, and the reason few settlers arrived to the islands was that there was no true economic value in the islands. In fact the only island that held true colonial power was Banaba due to the Phosphate deposits. Banaba was the only economic power in the islands, so became home to most of the settlers and trade in the islands. Sadly, these mines were emptied and the foreigners left, leaving behind few changes other than the destruction of the island's lands.
It was also during this time, in 1937, that famed American aviator Amelia Earhart went missing on a flight in the region. It is believed by some that she may have landed and/or crashed on Gardner Island (now known as Nikumaroro), which is in the Phoenix Islands and at the time under the jurisdiction of the United States.
Having little military presence in the islands, when the Japanese arrived in World War II, they easily took over a few of the islands in today's Kiribati, but the British and other Allied forces re-took these lands later in the war as the islands became stepping stones on the path to Japan. Tarawa Atoll was the recipient of one of these battles, which the Allies eventually won as they moved northwest from there.
After the war, Kiribati remained under British control, but by the 1970s independence was becoming more realistic. The Ellice Islands declared independence in 1975, creating the nation of Tuvalu and in 1978 the Gilbert Islands held their first general election, giving this island chain, along with the Line Islands and Phoenix Islands independence in 1979. The British had little interest in maintaining these islands as they had little economic value and few British settlers had called the islands home, so the transition was relatively smooth from the British perspective.
Since independence in 1979 Kiribati has, for the most part, remained politically stable. The only major issue is that the island of Banaba has run out of phosphate and their local economy has essentially crashed. Many of the residents have moved to Fiji and some are actively requesting that the island of Banaba join Fiji. Despite these calls for succession by Banaba, no legislature has been passed to make this move official. Today only about 300 people still live on the island of Banaba.