Local scholars assume that the Islamisation of Brunei started in the fifteenth century with the formation of the Bruneian Empire, a thalassocracy that covered the northern part of Borneo and Sulu.

The decline of the Bruneian Empire accelerated in the nineteenth century when Brunei gave much of its territory to the White Rajahs of Sarawak, resulting in its current small landmass and separation into two parts.

[6] The Austronesians began to develop a faith or cosmology around megalithism and then started to build social structure and agriculture as people settled down and tried to cultivate the land.

Ming dynasty accounts give detailed information about visits and tribute missions by rulers of Poni (modern Mandarin pronunciation) during the late 14th and early 15th century.

The warriors sacked the town, killed Makatunaw and his family, retrieved the stolen properties of the 10 datus, enslaved the remaining population of Udtuhan, and sailed back to Panay.

The first ruler chosen by the saudara to rule the newly founded state was Awang Alak Betatar, the son of Dewa Amas and the Sang Aji's daughter.

[21] According to Wang Zhenping, in the 1300s, the Yuan Dade nanhai zhi or "Yuan dynasty Dade period southern sea records" reported that Brunei administered Sarawak and Sabah as well as the Philippine kingdoms of: Butuan, Sulu, Ma-i (Mindoro), Malilu (Manila), Shahuchong (Siocon or Zamboanga), Yachen (Oton, once part of the Madja-as Kedatuan), and Wenduling (Mindanao),[22] which would regain their independence at a later date.

[24] In the 14th century, the Javanese manuscript Nagarakretagama, written by Prapanca in 1365, mentioned Barune as the constituent state of Hindu Majapahit,[25] which had to make an annual tribute of 40 katis of camphor.

In 1369, Sulu which was also formerly part of Majapahit, had successfully rebelled and then attacked Boni, and had invaded the Northeast Coast of Borneo[26] and afterward had looted the capital of its treasure and gold including sacking two sacred pearls.

[29][30] During the rule of Bolkiah, the fifth Sultan, the empire controlled the coastal areas of northwest Borneo (present-day Brunei, Sarawak and Sabah) and reached the Philippines at Sulu.

[b] In 1578, the Spanish took Sulu and in April attacked and captured Brunei itself, after demanding that the sultan cease proselytising in the Philippines and, in turn, allow Christian missionaries to be active in his kingdom.

Muslim migration from the Ottoman Caliphate, Egypt, Mecca and Arabia was so constant Melchor Davalos complained to the Spanish King of their presence in Borneo and the Philippines.

Persians and Arabs and Egyptians and Turks brought [Muhammad's] veneration and evil sect here, and even Moors from Tunis and Granada came here, sometimes in the armadas of Campson [Kait Bey], former Sultan of Cairo and King of Egypt...

Thus it seems to me that these Moros of the Philippine Islands [are] mainly those who, as had been said, come from Egypt and Arabia and Mecca, and are their relatives, disciples and members, and every year they say that Turks come to Sumatra and Borneo, and to Ternate, where there are now some of those defeated in the famous battle which Señor Don Juan de Austria won.To counteract Ottoman assistance to the Bruneians, Spain levied soldiers from their vassal states in Peru and Mexico, to supplement the Spanish troops sent to the Philippines.

The Resident became the most powerful person in the Sultanate as a result of this system, which essentially gave him substantial administrative authority equivalent to that of a Chief Justice and Menteri Besar combined.

[47] Significant changes in Brunei's history occurred as a result of Britain's efforts to increase its influence in the area in the late 19th century in reaction to geopolitical worries about the German Empire and the United States.

A significant turning point for Brunei was reached when Sultan Hashim Jalilul Alam Aqamaddin and the British government signed the Treaty of Protection with Sir Hugh Low on 17 September 1888, with the intention of obtaining security assurances from Lord Salisbury.

Due to this treaty, Brunei's foreign affairs were essentially handed over to Britain, preventing the Sultan from holding direct talks with North Borneo and Sarawak, two nearby states.

Sultan Hashim's disappointment with British support peaked in 1902 when he sent a heartfelt letter to King Edward VII, lamenting the lack of assistance his country had received since signing the treaty and the mounting difficulties it faced.

[49] Sultan Hashim's leadership was criticised by many British officials, and sentiment in the region began to shift toward Sarawak's government, which was perceived as offering more equitable taxes and better administration of Brunei's shrinking territory.

[52] As his dissatisfaction with British administration grew, Sultan Hashim expressed his willingness in 1903 to transfer Brunei to the Ottoman Empire due to what he saw as the oppression of Islam and the loss of territory.

In order to foster local governance, Sultan Ahmad Tajuddin pushed for the recruitment of 25 Bruneians to higher posts in the Brunei Administrative Service (BAS).

[75] Sultan backed the creation of regional defence units, such as the Brunei Volunteer Force, to help the British repel a Japanese invasion as tensions with Japan increased.

[80] Sultan Ahmad Tajuddin was portrayed by British envoy Malcolm MacDonald in July 1946 as a weak and indulgent king who was driven by excess and a lack of dedication to his royal duties.

[81] In Brunei Town, a welcome arch was built during MacDonald's visit, bearing the words "Restorer of Peace and Justice" beneath the Union Jack, emphasising the rights of the Sultan and his subjects.

[82] Because MacDonald's proposal to maintain Brunei's independence from Sarawak and North Borneo was supported by the Secretary of State for the Colonies, the Sultan was able to consolidate his control following World War II.

As a demonstration of his support for the political movement, Brunei developed its national song, "Allah Peliharakan Sultan," and adopted the Barisan Pemuda's (BARIP) flag.

[84] After ascending to the throne, Sultan Omar Ali Saifuddien III became the leader of the Islamic faith in Brunei, with a primary goal of improving the educational system.

[85] In 1950, Brunei began sending students to the Al-Juned Arabic School in Singapore, and by 1963, the first Bruneian graduated from Al-Azhar University in Egypt, marking a significant advancement in regional Islamic education.

Between 23 March and 6 April 1959, negotiations with British officials addressed key constitutional issues, including council meetings, elections, and the role of the Menteri Besar.