Preah Sihanouk province: History
=== Classical period (before 1700) ===
Prior to the city's creation in 1955, no recorded settlement on the peninsula existed that was larger than a traditional trading or fishing village. During the many centuries of pre-Angkorian and Angkorian history – from Funan to Chenla and during the Khmer Empire, regional trade was centered at O Keo (Vietnamese: Óc Eo) in the Mekong Delta, now the province of Rạch Giá in Vietnam. The township of Prei Nokor (Saigon) was a commercial center of the Khmer Empire.
The Chronicle of Samtec Cauva Vamn Juon – one of the 18th and 19th century Cambodian Royal Chronicles – briefly mentions the region as the country was split into three parts during a nine year civil war from 1476 to 1485: "In 1479, Dhammaraja took on the throne at Catumukh (Phnom Penh) and controlled the provinces of Samrong Tong, Thpong, Kompong Saom, Kampot up to the Bassak, Preah Trapeang, Kramuon Sar, Koh Slaket and Peam".
From the end of the 17th century, Cambodia lost control of the Mekong River as Vietnamese power expanded into the lower Mekong. During the Nguyen-Siamese War (1717–1718) a Siamese fleet burned the port of Kompong Som in 1717 but was defeated by the Vietnamese at Banteay Meas/Ha Tien. A Cambodian king of the late-18th century, Outey-Reachea III allied with a Chinese pirate, Mac-Thien-Tu, who had established an autonomous polity based in Ha Tien and controlled the maritime network in the eastern part of the Gulf of Thailand. Ha Tien was at a point where a river linking to the Bassac River flows into the Gulf of Thailand. Landlocked Cambodia tried to keep its access to maritime trade through Ha Tien. In 1757 Ha Tien acquired the ports of Kampot and Kompong Som as a reward for Mac's military support of the King of Cambodia. Until its destruction in 1771 the port developed into an independent duty-free entrepôt linked with several Chinese trading networks.
Alexander Hamilton, who traveled on the Gulf of Thailand in 1720, wrote that "Kompong Som and Banteay Meas (later Ha Tien) belonged to Cambodia, as Cochin-China was divided from Cambodia by a river (Bassac River) of three leagues broad." and "King Ang Duong constructed a road from his capital of Oudong to Kampot". Kampot remained the only international seaport of Cambodia. "The traveling time between Udong and Kampot was eight days by oxcart and four days by elephants."
French Résident Adhemard Leclère wrote: "...Until the 1840s, the Vietnamese governed Kampot and Péam [Mekong Delta], but Kompong Som belonged to Cambodia. The Vietnamese constructed a road from Ha Tien to Svai village - on the border with Kompong-Som - via Kampot."
The British Empire followed a distinct policy by the 1850s, seeking to consolidate its influence. Eyewitness reports give rare insights, as Foreign Secretary Lord Palmerston's agent John Crawfurd reports: "Cambodia was...the Keystone of our policy in these countries, - the King of that ancient Kingdom is ready to throw himself under the protection of any European nation...The Vietnamese were interfering with the trade at Kampot, and this would be the basis of an approach..." Palmerston concluded: "The trade at Kampot - one of the few remaining ports, could never be considerable, in consequence of the main entrance to the country, the Mekong, with all its feeders flowing into the Sea through the territory of Cochin China The country, too, had been devastated by recent Siam - Vietnam wars. …