A fragile ceasefire is holding after the most violent border clashes in more than a decade between Thailand and Cambodia, but human rights groups are urging a United Nations-led investigation into alleged war crimes and civilian harm.
The five-day conflict displaced more than 300,000 people and left at least 43 dead, in what observers say was the deadliest confrontation between the two neighbours in a decade.
The fighting also revealed the depth of global arms proliferation in South-East Asia.
Both sides deployed high-end weaponry from a variety of suppliers, ranging from China and Russia to Sweden and the United States.
Footage analysed by Stockholm International Peace Research Institute (SIPRI) and defence intelligence group Janes confirmed Cambodia's deployment of Chinese PHL-81 multiple rocket systems and several other systems, highlighting the deepening defence relationship between Phnom Penh and Beijing.
Cambodia also deployed Russian BMP-3 infantry fighting tanks, part of a $200 million arms deal signed in 2018, according to analysts.
Thailand countered with F-16 fighter jets, drones, Stryker infantry carriers, and Swedish-made Gripens aircraft, according to Thai Ministry of Defence statements and SIPRI's arms trade database.
"The level of hardware we saw from both sides this time is unprecedented," said Thailand-based military analyst Anthony Davis.
"We're not just talking about rifles and mortars. These are systems designed for high-intensity conflict."
Thailand's military dominance masks shifting alliances
Thailand boasts a $US5.73 billion ($8.87 billion) defence budget and 360,000 active military personnel, significantly outmatching Cambodia's 124,300 troops and ageing arsenal.
But that numerical advantage belies a more complex picture of shifting regional alliances.
While Thailand continues to straddle multiple arms suppliers, Cambodia has rapidly modernised its forces through deeper ties with China.
"Since the 2014 [Thai] military coup against Thaksin's sister, [then] prime minister Yingluck [Shinawatra], the US-Thailand defence relationship has somewhat cooled down," said Rahman Yaacob, an independent military analyst focused on South-East Asia.
Historically, Cambodia has relied on RM-70 multiple rocket launchers from the Czech Republic and large quantities of Soviet-era weapons acquired during the 1990s and 2000s.
But in recent years, it has pivoted more decisively toward Beijing.
"China has been Cambodia's most important security trading partner since around 2008," Mr Yaacob said.
"Due to human rights abuses in Cambodia, the Americans reduced military assistance."
Those abuses — chronicled by Human Rights Watch and the US State Department— include the dismantling of democratic institutions, a crackdown on opposition parties, and suppression of media and civil society under former prime minister Hun Sen.
Human rights groups and analysts warned that the recent use of long-range weaponry has made the conflict significantly more dangerous and raised concerns about future escalation.
"The Thai military certainly flagged the potential for Cambodia to use its Chinese 300mm PHL-03 multiple launch rocket systems, which pack a much bigger punch than the 122mm BM-21s and have a range of up to 130 kilometres," Mr Davis told the ABC.
"Had they been used, they could have hit provincial centres in the border provinces rather than just districts immediately on the border."
The Cambodian military said they did not use the PHL-03.
China's strategic balancing act
Beijing has armed both countries, while quietly discouraging outright escalation, analysts said.
Though Cambodia is often seen as China's closest military client in ASEAN, Thailand has also increasingly turned to Beijing, especially in the past decade.
"It's not as simple as China backs Cambodia and the US backs Thailand," said Mr Yaacob.
"It seems Thailand is moving away from the US to China because the systems are cheaper and less restricted."
He noted that China does not impose restrictions on buyers.
The US required buyers to request permission before using its Harpoon missiles — even during training.
Despite arming both sides, China does not want a full-blown war, said Siemon Wezeman, senior researcher at the Stockholm International Peace Research Institute.
"These things happen and both sides don't want to give in, don't want to say that they started it," said Mr Wezeman.
"You see macho guys going at each other, and somebody has to step in between — which luckily Malaysia did in this case."
War crime allegations and civilian impact
Cluster bomb use, school closures, and a high civilian death toll prompted global outcry.
Fortify Rights and Human Rights Watch have accused both sides of potential violations of international humanitarian law.
Civilian areas were struck by rockets and artillery, while Fortify Rights earlier this week pointed to evidence that Cambodia was "indiscriminately attacking" civilians.
"The use of unguided Grad rockets against civilian-populated areas is by its very nature indiscriminate, and may amount to war crimes," said Peter Bouckaert, senior director at Fortify Rights.
According to Human Rights Watch, at least 852 schools and seven hospitals in Thailand were closed for safety reasons.
Children were among those harmed in the crossfire.
Neither country is party to the Convention on Cluster Munitions, yet both are bound by broader obligations under the Geneva Conventions.
While initially denying Cambodian claims, a Thai military spokesperson later acknowledged that cluster munitions "can be utilised when necessary" — a statement that drew condemnation.
"Neither Thailand nor Cambodia appears to be paying attention to international humanitarian law at great expense to civilians," said John Sifton, Asia advocacy director at Human Rights Watch.
"Diplomatic efforts underway need to prioritise protecting civilians and civilian infrastructure."
Thai authorities also confirmed using F-16 jets and drones to launch air strikes against Cambodian positions.
Drone footage released by the Royal Thai Air Force showed strikes on what were described as Cambodian weapons depots.
The fighting has devastated communities along the 800-kilometre border, long disputed and dotted with ancient temple sites.
Many say this bout of violence surpassed previous episodes in intensity.
Thidarat Homhuan, 37, was one of thousands of people in Thailand's Surin province who fled their homes and sought refuge in makeshift shelters.
She told the AFP news agency the conflict felt more severe than the last major clashes in 2011.
"It wasn't this serious back then. People's houses weren't damaged like this. There were no announcements about civilians being injured," she said.
"This year is much worse — the number of deaths and injuries is really devastating."
Sweden's Gripen dilemma
The recent cross-border conflict was the first known use of the Swedish Saab Gripen fighter jets by the Royal Thai Air Force.Sweden's Foreign Minister Maria Malmer Stenergard told a defence publication this week that Thailand's request for additional jets had been withheld, stating, "the government is closely monitoring developments in the border conflict."
The jets used in the conflict were delivered under a two-phase deal. Thailand bought six Gripens valued at more than $1 billion in 2007.
They purchased another six in 2012.
The sale was originally defended by Swedish officials who said the aircraft were for reconnaissance, not attack.
But Mr Wezeman said that justification had not held up under scrutiny and jets have become a point of contention in Sweden's defence policy debate.
Sweden's export controls, which are supposed to limit sales to conflict zones, have come under fresh criticism.
Mr Wezeman said Sweden was far from alone in facing these dilemmas.
"Weapons have long life spans. You sell them today, and 10 or 15 years later, governments change, coups happen — and suddenly that gear is in a war zone," he said.
"This is quite normal. And once it's out there, you're no longer in control."
ABC/AFP
