Dark ages of Cambodia The Dark Ages of Cambodia covers the history of Cambodia from the fifteenth to the nineteenth century , a period of continued decline and territorial loss . Cambodia enjoyed a brief period of prosperity during the sixteenth century because its kings , who built their capitals in the region southeast of the Tonlé Sap along the Mekong River , promoted trade with other parts of Asia . This was the period when Spanish and Portuguese adventurers and missionaries first visited the country . But the Siamese conquest of the new capital at Longvek in 1594 marked a downturn in the country ' s fortunes and Cambodia became a pawn in power struggles between its two increasingly powerful neighbors , Siam and Vietnam . Vietnam ' s settlement of the Mekong Delta led to its annexation of that area at the end of the seventeenth century . Cambodia thereby lost some of its richest territory and was cut off from the sea . Such foreign encroachments continued through the first half of the nineteenth century because Vietnam was determined to absorb Khmer land and force the inhabitants to accept Vietnamese culture . Cambodia ' s struggle for survival , 1432 – 1867 . Post - Angkor Period . The more than four centuries that passed from the abandonment of Angkor around the mid - 15th century to the establishment of a protectorate under the French in 1867 are considered by historians to be Cambodia ' s " Dark Ages " , a period of economic , social , and cultural stagnation when the kingdom ' s internal affairs came increasingly under the control of its neighbors , the Thai ( Siam ) and the Vietnamese . By the mid - 19th century , Cambodia had become an almost helpless pawn in the power struggles between Siam and Vietnam and probably would have been completely absorbed by one or the other if France had not intervened , giving Cambodia a colonially dominated " lease on life . " Fear of racial and cultural extinction has persisted as a major theme in modern Cambodian thought . Establishment in 1979 of the People ' s Republic of Kampuchea , a Vietnamese - dominated satellite state , can be seen as the culmination of a process of Vietnamese encroachment that was already well under way by the seventeenth century . The process of internal decay and foreign encroachment was gradual rather than precipitous and was hardly evident in the fifteenth century when the Khmer were still powerful . Following the fall of Angkor Thom , the Cambodian court abandoned the region north of the Tonlé Sap , to Siam , never to return except for a brief interlude in the late sixteenth century . By this time however , the Khmer penchant for monument building had ceased . Older faiths such as Mahayana Buddhism and the Hindu cult of the god - king had been supplanted by Theravada Buddhism , and the Cambodians had become part of the same religious and cultural cosmos as the Siamese . This similarity did not prevent intermittent warfare between the two kingdoms , however . During the sixteenth century Cambodian armies , taking advantage of Siamese troubles with the Burmese , unsuccessfully invaded the Siamese kingdom several times . In the meantime , following the abandonment of the Angkorian sites , the few remaining Khmer survivors , with Siamese help , established a new capital several hundred kilometers to the southeast on the site of what is now Phnom Penh . This new center of power was located at the confluence of the Mekong and the Tonle Sab rivers . Thus , it controlled the river commerce of the Khmer heartland and the Laotian kingdoms and had access , by way of the Mekong Delta , to the international trade route s that linked the China coast , the South China Sea , and the Indian Ocean . A new kind of state and society emerged , more open to the outside world and more dependent on commerce as a source of wealth than its inland predecessor . The growth of maritime trade with China during the Ming dynasty ( 1368 – 1644 ) provided lucrative opportunities for members of the Cambodian elite who controlled royal trading monopolies . The appearance of Europeans in the region in the sixteenth century also stimulated commerce . First Contact with the West . The first reference of Cambodia in European documents was in 1511 by the Portuguese . King Ang Chan ( 1516 – 1566 ) , one of the few great Khmer monarchs of the post - Angkorian period , moved the capital from Phnom Penh to Lovek . Portuguese and Spanish travelers who visited the city , located on the banks of the Tonle Sab , a river north of Phnom Penh , described it as a place of fabulous wealth . The products traded there included precious stones , metals , silk and cotton , incense , ivory , lacquer , livestock ( including elephants ) , and rhinoceros horn ( prized by the Chinese as a rare and potent medicine ) . By the late sixteenth and early seventeenth centuries , Lovek contained flourishing foreign trading communities of Chinese , Indonesians , Malays , Japanese , Arabs , Spanish , and Portuguese . They were joined later in the century by the English and the Dutch . It was during this period ( in 1555 - 1556 ) that the Portuguese friar Gaspar da Cruz made the first attempt to introduce Christianity into the country . According to his own account , his attempt was a complete failure due to the strong " Bramene " conviction of the king and the ruling classes ; however , the brief report he made of his mission offers an interesting insight into the nations ' religious practices of the time . Because the representatives of practically all these nationalities were pirates , adventurers , or traders , this was an era of stormy cosmopolitanism . Hard - pressed by the Siamese , to repay his debts , King Sattha ( 1576 – 94 ) surrounded himself with a personal guard of Spanish and Portuguese mercenaries , and in 1593 asked the Spanish governor of the Philippines for aid . Attracted by the prospects of establishing a Spanish protectorate in Cambodia and of converting the monarch to Christianity , the governor sent a force of 120 men , but Lovek had already fallen to the Siamese when they arrived the following year . The Spanish took advantage of the extremely confused situation to place one of Sattha ' s sons on the throne in 1597 . Hopes of making the country a Spanish dependency were dashed , however , when the Spaniards were massacred two years later by an equally belligerent contingent of Malay mercenaries . The Siamese , however , had dealt a fatal blow to Cambodian independence by capturing Lovek in 1594 . With the posting of a Siamese military governor in the city , a degree of foreign political control was established over the kingdom for the first time . Cambodian chronicles describe the fall of Lovek as a catastrophe from which the nation never fully recovered . Siam ruled Cambodia for most of the next 300 years , finally losing Angkor Wat to the French in 1907 after holding it for over 450 years . Domination by Siam and by Vietnam . More than their conquest of Angkor a century and a half earlier , the Siamese capture of Lovek marked the beginning of a decline in Cambodia ' s fortunes . One possible reason for the decline was the labor drain imposed by the Siamese conquerors as they marched thousands of Khmer peasants , skilled artisans , scholars , and members of the Buddhist clergy back to their capital of Ayutthaya . This practice , common in the history of Southeast Asia , crippled Cambodia ' s ability to recover a semblance of its former greatness . A new Khmer capital was established at Odongk ( Udong ) , south of Lovek , but its monarchs could survive only by entering into what amounted to vassal relationships with the Siamese and with the Vietnamese . In common parlance , Siam became Cambodia ' s " father " and Vietnam its " mother . " By the late fifteenth century , the Vietnamese - who , unlike other Southeast Asian peoples , had emerged from the Sinic civilization sphere - had completely absorbed the once most powerful maritime kingdom of Champa in central Vietnam . Thousands of Chams fled into Khmer territory . By the early seventeenth century , the Vietnamese had reached the Mekong Delta , which was inhabited by Khmer people . In 1620 the Khmer king Chey Chettha II ( 1618 – 28 ) married a daughter of Nguyễn Phúc Nguyên , one of the Nguyễn lords ( 1558 – 1778 ) , who ruled southern Vietnam for most of the period of the Lê Dynasty ( 1428 - 1788 ) . Three years later , Chey Chettha allowed the Vietnamese to establish a custom - house at Prey Nokor , near what is now Ho Chi Minh City ( until 1975 , Saigon ) . By the end of the seventeenth century , the region was under Vietnamese administrative control , and Cambodia was cut off from access to the sea . Trade with the outside world was possible only with Vietnamese permission . There were periods in the seventeenth and the eighteenth centuries , when Cambodia ' s neighbors were preoccupied with internal or external strife , that afforded the beleaguered country a breathing spell . The Vietnamese were involved in a lengthy civil war until 1672 ( see the Trịnh – Nguyễn War for details ) , but upon its conclusion the Nguyễn Lords , who ruled in the south , promptly annexed sizable areas of Cambodian territory in the region of the Mekong Delta . For the next one hundred years they used the alleged mistreatment of Vietnamese colonists in the delta as a pretext for their continued expansion , as well as territorial concessions from inter - royalty marriage . By the end of the eighteenth century , they had extended their control to include the area encompassed in the late 1980s by the Socialist Republic of Vietnam ( Vietnam ) . Siam , which might otherwise have been courted as an ally against Vietnamese incursions in the eighteenth century , was itself involved in a new conflict with Burma . In 1767 the Siamese capital of Ayutthaya was besieged and destroyed . The Siamese quickly recovered , however , and soon reasserted their dominion over Cambodia . The youthful Khmer king , Ang Eng ( 1779 – 96 ) , a refugee at the Siamese court , was installed as monarch at Odongk by Siamese troops . At the same time , Siam quietly annexed Cambodia ' s three northernmost provinces . In addition , the local rulers of the northwestern provinces of Batdambang and Siemreab ( Siemreap ) became vassals of the Siamese king , and these areas came under the Siamese sphere of influence . A renewed struggle between Siam and Vietnam for control of Cambodia in the nineteenth century resulted in a period when Vietnamese officials , working through a puppet Cambodian king , ruled the central part of the country and attempted to force Cambodians to adopt Vietnamese customs . Several rebellions against Vietnamese rule ensued . The most important of these occurred in 1840 to 1841 and spread through much of the country . After two years of fighting , Cambodia and its two neighbors reached an accord that placed the country under the joint suzerainty of Siam and Vietnam . However , fearful of a longer past dominated by Thai incursions , under a separate attempt , Cambodia offered to reside under Vietnamese protectorship . At the behest of both countries , a new monarch , Ang Duong ( 1848 – 59 ) , ascended the throne and brought a decade of peace and relative independence to Cambodia . In their arbitrary treatment of the Khmer population , the Siamese and the Vietnamese were virtually indistinguishable . The suffering and the dislocation caused by war were comparable in many ways to similar Cambodian experiences in the 1970s . But the Siamese and the Vietnamese had fundamentally different attitudes concerning their relationships with Cambodia . The Siamese shared with the Khmer a common religion , mythology , literature , and culture . The Chakri kings at Bangkok wanted Cambodia ' s loyalty , tribute and land , but they had no intention of challenging or changing its people ' s values or way of life . The Vietnamese viewed the Khmer people as barbarians to be civilized through exposure to Vietnamese culture , and they regarded the fertile Khmer lands as legitimate sites for colonization by settlers from Vietnam . French Protectorate 1867 - 1953 . France ' s interest in Indochina in the nineteenth century grew out of its rivalry with Britain , which had excluded it from India and had effectively shut it out of other parts of mainland Southeast Asia . The French also desired to establish commerce in a region that promised so much untapped wealth and to redress the Vietnamese state ' s persecution of Catholic converts , whose welfare was a stated aim of French overseas policy . The Nguyễn Dynasty ' s repeated refusal to establish diplomatic relations and the violently anti - Christian policies of the emperors Minh Mạng ( 1820 – 41 ) , Thiệu Trị ( 1841 – 47 ) , and Tự Đức ( 1848 – 83 ) impelled the French to engage in gunboat diplomacy that resulted , in 1862 , in the establishment of French dominion over Saigon and over the three eastern provinces of the Cochinchina region . In the view of the government in Paris , Cambodia was a promising backwater . Persuaded by a missionary envoy to seek French protection against both the Thai and the Vietnamese , King Ang Duong invited a French diplomatic mission to visit his court . The Thai , however , pressured him to refuse to meet with the French when they finally arrived at Udong in 1856 . The much - publicized travels of the naturalist Henri Mouhot , who visited the Cambodian court , rediscovered the ruins at Angkor , and journeyed up the Mekong River to the Laotian kingdom of Luang Prabang from 1859 to 1861 , piqued French interest in the kingdom ' s alleged vast riches and in the value of the Mekong as a gateway to China ' s southwestern provinces . In August 1867 , the French concluded a treaty with Ang Duong ' s successor , Norodom ( 1859 – 1904 ) . This agreement afforded the Cambodian monarch French protection ( in the form of a French official called a résident — in French resident ) in exchange for giving the French rights to explore and to exploit the kingdom ' s mineral and forest resources . Norodom ' s coronation , in 1868 , was an awkward affair at which both French and Thai representatives officiated . Although the Thai attempted to thwart the expansion of French influence , their own influence over the monarch steadily dwindled . In 1869 the French concluded a treaty with the Thai that gave the latter control of Batdambang Province and of Siemreab Province in exchange for their renunciation of all claims of suzerainty over other parts of Cambodia . Loss of the northwestern provinces deeply upset Norodom , but he was beholden to the French for sending military aid to suppress a rebellion by a royal pretender . In June 1884 , the French governor of Cochinchina went to Phnom Penh , Norodom ' s capital , and demanded approval of a treaty with Paris that promised far - reaching changes such as the abolition of slavery , the institution of private land ownership , and the establishment of French résidents in provincial cities . Mindful of a French gunboat anchored in the river , the king reluctantly signed the agreement . Local elites opposed its provisions , however , especially the one dealing with slavery , and they fomented rebellions throughout the country during the following year . Though the rebellions were suppressed , and the treaty was ratified , passive resistance on the part of the Cambodians postponed implementation of the reforms it embodied until after Norodom ' s death .