This articleneeds additional citations forverification. Please helpimprove this article byadding citations to reliable sources. Unsourced material may be challenged and removed. Find sources: "Castilian War" – news ·newspapers ·books ·scholar ·JSTOR(February 2023) (Learn how and when to remove this message)

Castilian War
Bruneian forces fighting Spanish forces
Date 16 April – 26 June 1578 Location Borneo,Mindanao, andSulu Result Status quo ante bellum
Belligerents
Bruneian Empire Sulu Sultanate Maguindanao Supported by: Ottoman Empire Portuguese Empire	Spanish Empire Captaincy General of the Philippines Bruneian defectors
Commanders and leaders
Sultan Saiful Rijal Bendahara Sakam Muhammad ul-Halim Datu Bangkaya Pengiran Kestani[note 1]	Francisco de Sande Pengiran Seri Lela   or  † Pengiran Seri Ratna †
Units involved
Bruneian Army	Spanish Army 200 Spaniards 200 Mexicans 1,500 Filipinos 300 Bruneians
Strength
around ~1,000–5,000 warriors[2][3] 62 guns 50 ships	2,200 men 40 ships
Casualties and losses
Unknown 170artillery pieces; 27ships andgalleys captured[4]	Unknown; presumably heavy[5] 17 men dead(by dysentery)[6]

TheCastilian War, also called theSpanish Expedition to Borneo, was a conflict between theSpanish Empire and several Muslim states inSoutheast Asia, including the Sultanates ofBrunei,Sulu, andMaguindanao. It is also considered as part of theOttoman-Habsburg Wars. This war is the beginning of relations between the Ottoman state and the Sultanate of Brunei in 1560 to 1578.

TheSpanish settlements soon began to encroach on the aspirations that Brunei had in the Philippines. The Spanish wanted to Christianize the Muslim-majority regions of the southern Philippines and diminish Bruneian influence. Between 1485 and 1521,Sultan Bolkiah's influence had reached the Manila Bay region, as recorded by the Spaniards during their encounter withPrince Ache in 1521, who was Bolkiah's grandson. The Muslim presence in the region was also strengthened by the arrival of traders andmissionaries from the areas ofMalaysia andIndonesia.^[7]

DespiteBruneian influence, Spanish colonization continued in the archipelago. In 1571, Miguel López launched an expedition from his capital in Cebu to conquer and Christianize the city ofManila, which became the new capital for the Spanish administration. Furthermore, theVisayan peoples of Panay andCebu (who historically fought against Brunei's allies of Sulu and Maynila) aligned themselves with the Spaniards against Brunei. In 1576,Governor-GeneralFrancisco de Sande sent a request to meet with SultanSaiful Rijal, expressing a desire for good relations with Brunei. However, In 1573, the Governor-General De Sande demanded both permission to proselytize Christianity in the region, and an end to Brunei's proselytizing of Islam. De Sande regarded Brunei as a threat to Spanish presence and religious efforts in the region, stating that "theMoros from Borneo preach the doctrine ofMohammed, converting all the Moros of the islands".^[8][9]

Governor-General Francisco de Sande officially declared war against Brunei in 1578, and began preparations for an expedition to Borneo. De Sande assumed the title ofCapitán-General and assembled a fleet carrying 200 Spaniards, 200 Mexicans, 1,500 nativeFilipinos (Luzones), and 300 Borneans.^[10] The ethnic composition of the Spanish force was shown to be diverse by later documents that stated the infantry was made up ofmestizos,mulattoes, and "Indians" (from Peru and Mexico), led by Spanish officers who had previously fought with native Filipinos in military campaigns across Southeast Asia.^[11] The expedition began their journey in March, and the Bruneian campaign was one of several that was undertaken at the time, including action inMindanao andSulu.^[12][13]

While the Spanish were unable to immediately subjugate Brunei, they did manage to prevent it from regaining a foothold in Luzon.^[14] Relations between the two nations later improved and trade resumed, as evidenced by a 1599 letter from Governor-GeneralFrancisco de Tello de Guzmán in which he asked for a return to a normal relationship.^[15]

As a result of the conflict, Brunei ceased to be anempire at sea. It gradually set aside its policies of territorial expansion and developed into a city-state, surviving to the modern day as the oldest continuously Islamic political entity.^[16] Despite this, this wouldn't be the last time Spain fought the Bruneians as they fought again in theTwenty Years' War.

• Wars involving the Philippines
• Wars involving Spain
• Wars involving Brunei
• Ottoman–Spanish conflicts
• Military history of the Pacific Ocean

• CS1 Spanish-language sources (es)
• Articles with short description
• Short description is different from Wikidata
• Use British English from June 2017
• All Wikipedia articles written in British English
• Use dmy dates from June 2017
• Articles needing additional references from February 2023
• All articles needing additional references