Colonial maps and an ancient temple: the story behind the bloody conflict between Thailand and Cambodia

A Cambodian soldier stands guard near a destroyed building on the Thai-Cambodia border. He watches as a team of soldiers and officials inspect the site.

- Author, James Lewis
- Author title, BBC World Service
- Author, BBC Thai Service
- Author title, BBC
52 minutes

Simmering tensions between Thailand and Cambodia have flared again on their shared border, derailing the fragile ceasefire supported by US President Donald Trump.

Official sources in both countries said at least five Thai soldiers and nine Cambodian civilians were killed and dozens injured in the latest clashes that began on Monday.

After dozens of people died in July, these are the worst clashes since the ceasefire was agreed.

The dispute between the two countries dates back more than 100 years, when borders were drawn after the French occupation of Cambodia.

But it is also influenced by a centuries-old cultural rivalry.

At the center of it all is Preah Vihear, an 11th-century Hindu temple perched on a cliff in the Dângrêk Mountains, which form the border between the two countries.

Cultural rivalry

For centuries, power in Southeast Asia was determined by the rise and fall of empires.

From the 9th to the 15th centuries, the Khmer Empire, whose heart lay in what is now Cambodia, ruled much of the region, including large areas of what is now Thailand, Laos and Vietnam.

But with the decline of the Khmer Empire, new powers emerged.

In 1431, the Kingdom of Ayutthaya, the forerunner of the Kingdom of Siam and modern-day Thailand, invaded and conquered Angkor, the capital of the Khmer Empire, and began occupying the western territories of Cambodia.

In the centuries that followed, Cambodia found itself caught between ambitious neighbors and its sovereignty was repeatedly questioned.

In the 19th century, a new external actor appeared: France.

France, which already controlled South Vietnam, pressured Cambodia to accept protectorate status in 1863.

At the beginning of the 20th century, France further consolidated its power in the region through two treaties with the Kingdom of Siam in 1904 and 1907, which provided for the cession of large territories to French Indochina.

These treaties established the principle that in the eastern part of the Dângrêk Mountains the border should run along the watershed.

However, the mapping process carried out by French surveyors resulted in ambiguities, particularly around Preah Vihear, which is very close to the planned watershed boundary.

During World War II, Thailand regained some of the territory it had lost under the 1907 treaty, including the site of the temple.

After the war, Thailand was forced to return the territory it had gained to French control, although Thai troops re-entered the Preah Vihear area in 1947.

Six years later, Cambodia gained independence from France and in 1959 filed a lawsuit with the International Court of Justice (ICJ) to confirm its territorial sovereignty over the temple.

At the heart of the case before the International Court of Justice were two contradictory interpretations of the border.

Cambodia was based on a French colonial map derived from the treaties of 1904 and 1907, which was able to place the temple on the Cambodian side.

Thailand argued that it had never accepted this map or, if it had accepted it, would have done so only on the false assumption that the specified boundary was in fact the watershed.

In 1962, the ICJ ruled in favor of Cambodia’s position on the grounds that both sides had accepted and effectively used the existing border for several decades.

Map showing the border between Thailand and Cambodia and the disputed territories.

The temple was virtually inaccessible during the Cambodian civil wars and the Khmer Rouge era and was only reopened to the public in the 1990s.

However, tensions rose again in 2008 when Cambodia managed to add Preah Vihear to the UNESCO World Heritage List.

Thailand protested, claiming the listing had implications for sovereignty, and armed clashes broke out along the border between 2008 and 2011, leaving at least 20 people dead and thousands displaced.

Cambodia again turned to the International Court of Justice to seek clarification of the 1962 ruling.

The court ordered the withdrawal of troops in 2012 and confirmed in 2013 that the temple and its surroundings were on Cambodian territory.

Evacuations when fighting breaks out

Thailand and Cambodia have blamed each other for sparking the latest wave of violence that has led to the evacuation of hundreds of thousands of people on both sides.

Thai Prime Minister Anutin Charnvirakul said his country “never wanted violence” but would use “all necessary means to preserve its sovereignty,” while former Cambodian leader Hun Sen accused Thai “invaders” of provoking the retaliation.

Trump said Tuesday he would “make a call” to “stop a war between two very powerful countries.”

It is not clear what the outcome of this situation will be.

Although there have been serious armed conflicts in the past, these calmed down relatively quickly.

In July, BBC correspondent Jonathan Head believed it would happen again.

However, he warned that both countries currently lack leaders with the strength and confidence to end this confrontation.