Why are Thailand and Cambodia attacking each other? The fighting has already left at least 12 dead.

BarcelonaThe Thai and Cambodian armies clashed on Thursday along their shared border. The fighting, which left at least 12 dead and 30 wounded, marks a significant escalation of the long-standing border dispute between the two countries.

Around 8:00 a.m. local time, Thai and Cambodian soldiers exchanged fire on the grounds surrounding the Ta Muen Thom temple, which separates the Thai province of Surin from the Cambodian province of Oddar Mean Chey. Both Thailand and Cambodia, which share a 800-kilometer border, accused each other of instigating the attacks. Within hours, the fighting spread to at least six points along the border. Thai forces launched airstrikes against Cambodian military targets, and the Cambodian army fired shells at Thai positions.

"F-16s have launched attacks! Cambodian military posts of the 8th and 9th Divisions (Special Forces Commandos) have been destroyed," the Thai military announced in a Facebook post, subsequently ordering a complete closure of the border. Cambodia's Ministry of Defense condemned the "brutal military aggression" and vowed to defend itself. Thailand has evacuated 40,000 civilians, while both governments are urging people to leave the area.

Both countries blame each other for initiating the offensive. Thailand accuses Cambodia of sending soldiers armed with rocket launchers into Surin province, while Cambodian Senate President and former leader Hun Sen claims Bangkok began the attacks with an "invading balloon."

A colonial border

The territorial dispute dates back to 1907, when the then Kingdom of Siam (present-day Thailand) and France, which occupied the territory of what is now Cambodia, signed a treaty to define their borders. It remained unclear who owned the area in question. "When the French withdrew from Cambodia in 1952, Thai troops occupied part of the border area, including the Preah Vihear temple," CIDOB researcher Inés Arco, who specializes in East Asia, explained to ARA. At the time, Cambodia took the case to the International Court of Justice, which recognized its sovereignty over the temple but did not clarify its control of the surrounding area. "As Thailand had never protested that this area was outside its jurisdiction on French maps, the court interpreted this as an admission of agreement," adds Just Castillo Iglesias, professor of East Asian studies at the UAB. "Cambodia sees itself in a position of strength because it has the international legality of its gang," Castillo adds, while Bangkok does not fully accept the verdict, interpreting it as a territorial loss.

The conflict remained simmering until 2008, when the temple's UNESCO registration reignited the dispute, provoking a wave of nationalism in Thailand and clashes that left around thirty dead. The fighting forced ASEAN (the Association of Southeast Asian Nations) to intervene to secure a diplomatic ceasefire.

The resurgence in a context of instability

The clash between Thailand and Cambodia comes a day after a Thai soldier lost his right leg after stepping on a landmine in border territory in Ubon Ratchathani, the second such incident this month. In response, Thailand recalled its ambassador from Cambodia and expelled the Cambodian ambassador from Bangkok, accusing Phnom Penh of planting mines on Thai territory and violating the Ottawa Convention, which bans landmines. But tensions have been rising since late May after a Cambodian soldier was killed in an exchange of fire between the two militaries.

The crisis erupts amid political instability in Thailand, following the disqualification of the current Prime Minister, Paetongtarn ShinawatraFollowing the leak of a conversation between him and former Cambodian Prime Minister Hun Sen. Meanwhile, Cambodia is taking advantage of the instability in its neighboring country to strengthen its position in the territorial dispute over Preah Vihear.

Tensions have lasted for weeks or months, but have not gone beyond isolated armed incidents.