Castille War The Castille War ( My . : " Perang Kastila " ; Jawi : ڤراڠ كستيلا , Sp . : " Expedición de Brunei " ) was a military conflict between Brunei and Spain in 1578 . Background . Since the middle of the 16th century , Europeans were eager to gain a foothold in South East Asia because of the spice trade . During that period , all the land routes from the Middle East to South East Asia were controlled by the Arabs and Turks . The Europeans attempted to control the maritime route to South East Asia so they could trade with the Malays . At the time , Brunei Darussalam was an established empire ranging from the Philippines to Borneo Island . It was during the reign of Sultan Saiful Rijal when the Castille War broke out . He faced two main problems which was that the Spanish wanted to spread Christianity and invade the Philippines . In 1565 , the Spanish captured Cebu in the Philippines . They turned it into a trading post and a center for spreading Christianity and Hispanicization . Because of this , Spain ' s goals came to clash with those of their main rival , Brunei . Between 1485 and 1521 , the Sultanate of Brunei had established the state of Kota Serudong ( in modern - day Manila ) as a Bruneian satellite state . Islam was further strengthened by the arrival to the Philippines of traders and proselytizer s from present - day Malaysia and Indonesia . The multiple states that existed in the Philippines simplified Spanish colonization . In 1571 Spanish conquistador Miguel Lopez de Legazpi founded Manila , which was made the capital of the Philippine Islands , also becoming a hub for spreading Christianity . In 1576 , the Spanish Governor in Manila was Francisco de Sande . He sent an official mission to neighbouring Brunei to meet Sultan Saiful Rijal . He explained to the Sultan that they wanted to have good relations with Brunei and also asked for permission to spread Christianity in Brunei . At the same time , he demanded an end to Brunei proselytisim of Islam in the Philippines . Sultan Saiful Rijal would not agree to these terms and also expressed his opposition to the evangelization of the Philippines , which he deemed part of Dar al - Islam . In reality , De Sande regarded Brunei as a threat to the Spanish presence in the region , claiming that " the Moros from Borneo preach the doctrine of Mahoma , converting all the Moros of the islands " . Spain declared war in 1578 , attacking and capturing Brunei ’ s capital at the time , Kota Batu . This was achieved as a result in part of the assistance rendered to them by two noblemen , Pengiran Seri Lela and Pengiran Seri Ratna . The former had travelled to Manila to offer Brunei as a tributary of Spain for help to recover the throne usurped by his brother , Saiful Rijal . The Spanish agreed that if they succeeded in conquering Brunei , Pengiran Seri Lela would indeed become the Sultan , while Pengiran Seri Ratna would be the new Bendahara . In March 1578 , the Spanish fleet , led by De Sande himself , acting as Capitán General , started their journey towards Brunei . The expedition consisted of 400 Spaniards , 1 , 500 Filipino natives and 300 Borneans . The campaign was one of many , which also included action in Mindanao and Sulu . The Spanish succeeded in invading the capital on 16 April 1578 , with the help of Pengiran Seri Lela and Pengiran Seri Ratna . The Sultan Saiful Rijal and Paduka Seri Begawan Sultan Abdul Kahar were forced to flee to Meragang then to Jerudong . In Jerudong , they made plans to chase the conquering army away from Brunei . The Spanish suffered heavy losses due to a cholera or dysentery outbreak . They were so weakened by the illness that they decided to abandon Brunei to return to Manila on 26 June 1578 , after just 72 days . Before doing so , they burned the mosque , a high structure with a five - tier roof . Pengiran Seri Lela died in August – September 1578 , probably from the same illness that had afflicted his Spanish allies , although there was suspicion he could have been poisoned by the ruling Sultan . Seri Lela ' s daughter left with the Spanish and went on to marry a Christian Tagalog , named Agustín de Legazpi de Tondo . The local Brunei accounts differ greatly from the generally accepted view of events . The " Castilian War " entering the national conscience as a heroic episode , with the Spaniards being driven out by Bendahara Sakam , supposedly a brother of the ruling Sultan , and a thousand native warriors . This version , nevertheless , is disputed by most historians and considered a folk - hero recollection , probably created decades or centuries after . Notwithstanding their retreat from Brunei , Spain managed to keep Brunei from gaining a foothold in Luzon . Aside this , a few years later , they were ready to trade again with the Sultanate , as evidenced by a letter from Don Francisco de Tello de Guzmán , Governor General of Manila , dated 1599 asking for a return of normal relationship .