BANGKOK, Thailand -- China let loose their robot dogs of war -- shooting machine guns mounted on their backs -- during Beijing's biggest military exercise in Cambodia May 16-30, amid a smoldering rivalry along the Gulf of Thailand used by China's Navy and the U.S. 7th Fleet's nuclear-powered aircraft carrier.

The 15-day Golden Dragon 2024 exercises were led by China's People's Liberation Army (PLA) Southern Theater Command guiding Beijing's closest ally in Southeast Asia, the Royal Cambodian Armed Forces.

The U.S. and China are taking turns wooing Cambodia's West Point-educated prime minister with guns, money and friendship, but the Chinese are scoring most of the rewards.

Just as Beijing's biggest military exercise in Cambodia ended, U.S. Defense Secretary Lloyd Austin arrived in Phnom Penh to offer military assistance and mend the often rough diplomatic relations between the two former wartime enemies.

Mr. Austin met Cambodia's Prime Minister Hun Manet and Defense Minister Tea Seiha during his one-day stop on June 4, after attending a Singapore defense forum where he met his Chinese counterpart Adm. Dong Jun.

Coincidentally, Hun Manet was the U.S. Military Academy at West Point's first Cambodian cadet in 1999, 24 years after Mr. Austin graduated from there in 1975.

That may have smoothed the way for their talks which likely included Beijing's military advances in Cambodia amid the smoldering rivalry along the Gulf of Thailand, which is used by China's Navy and the U.S. 7th Fleet's nuclear-powered aircraft carrier.

The U.S. is also concerned with Cambodia's alleged human rights abuses and crackdown on political and press freedom, and plans by Phnom Penh and Beijing to dig a canal from the Mekong River to the Gulf of Thailand.

Mr. Hun Manet was blatantly boosted into power last year by his authoritarian father, former prime minister Hun Sen, who consistently welcomed China's increase in Cambodia's economic, diplomatic, and military affairs.

China's Golden Dragon 2024 military exercises in Cambodia were "the first since Hun Manet became prime minister, indicating that he is continuing to expand his father's embrace of China," said Craig Etcheson, an author and researcher about Cambodian.

Golden Dragon included "more than 1,300 Cambodian troops, more than 700 Chinese troops, three large warships, and 11 Cambodian warships," said Cambodian Maj. Gen. Thong Solimo.

Maneuvers also involved two helicopters, and nearly 70 armored vehicles and tanks, accompanied by weaponized robot dogs.

Chinese-led live-fire exercises performed anti-terrorism and rescue operations.

Cambodians learned how to use "Chinese sniper rifles" including "the QBU-191, the latest precision rifle in service with the PLA," China's Global Times reported.

Phnom Penh agreed to host Beijing's first Golden Dragon in 2016 after cancelling U.S.-Cambodian Angkor Sentinel military exercises.

Much of the Chinese weaponry and equipment arrived by sea, unloaded at Cambodia's Sihanoukville Port along the gulf.

"We can definitely say that the U.S.-China rivalry has spread to the Gulf of Thailand," said Paul Chambers, a Naresuan University lecturer on security and politics in Thailand and Cambodia.

He pointed to Cambodia's Ream Naval Base which received Chinese financing to expand along the gulf.

Ream can be used by Chinese and some international shipping, but Washington fears Cambodia could eventually allow Chinese warships to base there, heightening tensions in the Gulf of Thailand which opens to the internationally disputed South China Sea.

"With China able to use Ream for its naval military vessels, and Dara Sakor [a private airfield in Cambodia leased to Chinese] for its air force, Cambodia has become a key geopolitical chess piece of Beijing in Southeast Asia," Mr. Chambers said in an interview.

"Yes, the U.S.-China rivalry has extended to the Gulf of Thailand," said Arizona State University associate professor Sophal Ear who researches Cambodia's politics.

"Thailand's military relationship with the U.S. is built on decades of established alliances, joint exercises, and strategic partnerships," he said.

Thailand annually conducts large-scale military exercises with the Pentagon, and routinely allows the U.S. Navy to dock at facilities along the shallow Gulf of Thailand.

For example in April, nuclear-powered Nimitz-class aircraft carrier USS Theodore Roosevelt, armed with missile launchers, docked at Thailand's Laem Chabang port near Bangkok, a routine which began in 2018 in the U.S. 7th Fleet's area.

"We are here to make sure we are ready to respond to any crisis in the area," Carrier Strike Group Nine Commander, Rear Admiral Christopher Alexander, said after docking.

"We are here to deter aggression," he said, accompanied by the USS Theodore Roosevelt's more than 80 warplanes, including anti-submarine aircraft, strike fighters, and planes equipped with electronic countermeasures.

The aircraft carrier, powered by two nuclear reactors, brought 5,000 crewmembers from San Diego, California, bolstering the U.S. Pacific Fleet in the Indo-Pacific region. 

"Tasked with maintaining open sea lanes of trade and communications, USS Theodore Roosevelt is capable of projecting air superiority to all points of the globe," the Navy said on its website.

In Cambodia meanwhile, China's low-slung, flat-backed robot dogs became a big hit during the joint military exercises.

In online photographs and videos posted by participants, grinning Chinese and Cambodian uniformed troops cluster around a robodog which is armed with a heavy black machine gun bolted onto the quadruped's flat back.

A Chinese officer holds a CD-sized, black box with two short, protruding antennae, resembling a Wi-Fi router, remotely controlling the robot.

When the crouching machine slowly stands up, several Cambodian officers back away, laughing nervously until it achieves a four-legged standing canine position.

Video from one robot dog's front camera shows the robodog maneuvering through a makeshift maze of green netting and scaffolding.

Two accompanying Cambodian soldiers aim their assault rifles into the maze, ready to advance alongside the machine.

The robot dog exits the green maze and, backed by Cambodian armored personnel carriers, stalks across flat dry land blasting its weapon, causing black smoke to jettison from its barrel.

The mounted machine gun displays a curved magazine for bullets and a trigger, enabling the gun to be taken off the robodog if a human wants to shoot it.

Lettering on the robot dog's gray surface identifies it as "B1 Unitree".

Unitree Robotics is "a Chinese startup that has been developing its own line of robot dogs since 2016," reported Cyberguy.com, a site for computer news.

"Unitree's latest product is the B2, a sleek and powerful robot that can run faster, jump higher, and carry more weight than its predecessor, the B1," it reported.

The B2 has two high-definition optical cameras, a pair of depth-sensing cameras, and a Lidar [Light Detection and Ranging] remote sensing module that provides it with a 360-degree view of its surroundings.

A B2 robot dog's energy comes from a swappable, lithium battery, boosting its speed to nearly 20 feet per second, twice as fast as the B1.

The robot can function autonomously after programming or by remote control, and is shown climbing stairs, and remaining balanced while walking across obstacles.

Robodogs speak Chinese through a speaker and can hear via a microphone, allowing them "to communicate with humans and other robots," Cyberguy said.

The B2 is a "brand new intelligent species" which can walk for five hours carrying an 18-pound load, said Unitree Robotics, based in Hangzhou near Shanghai, China.

The B2's "control and perception" has a "standard configuration: Intel Core i5 Platform Function, Intel Core i7 User Development," it said on Unitree's website.

"Unitree B2 continues to evolve every day with the acceleration of AI," Unitree told 20,000 followers on X.

Futurism, a New York-based website reporting technological developments, described the "terrifying gun-toting robodogs" as "a dystopian vision of what the future of warfare could look like.

"Last year, the Pentagon announced that the U.S. Army is considering arming remote-controlled robot dogs with state-of-the-art rifles as part of its plan to 'explore the realm of the possible' in the future of combat," Futurism reported.

"A U.S.-based military contractor called Ghost Robotics has already showed off such a robot dog, outfitted with a long-distance rifle," it said.

China's mechanical deadly dogs performing in Cambodia intrigued analysts.

"While the display of robotic dogs is more a demonstration of technological capability than a direct threat, it does signify China's advancements in military technology," Mr. Sophal Ear said in an interview.

"The U.S. should take note of these developments, as part of the broader context of China's growing military capabilities and innovation in unmanned systems and AI-driven warfare technologies."

Beijing's military exercises with Phnom Penh means "increased military presence and surveillance, potential flashpoints for conflict, and a heightened state of alert among regional nations. This rivalry could also impact regional trade routes and economic stability," Mr. Sophal Ear said.

"Numerous U.S. defense contractors have produced operational combat robot dogs, and the U.S. military has been actively evaluating these systems," Mr. Etcheson said in an interview.

"I see the recent display in Cambodia by China as an attempt to show that they are keeping pace with the technological advancement of their rival [U.S.] power," Mr. Etcheson said.

China's expanding influence in Cambodia may protect Phnom Penh from Washington and other critics.

"China has become the Cambodian regime's guarantee against interference from the West's insistence on compliance with international law and a measure of respect for human rights," said Rich Garella, an American former press secretary for Cambodian opposition leader Sam Rainsy.

"The regime is sacrificing its sovereignty and becoming a vassal state of China, as it was for centuries in the past," Mr. Garella said in an interview.

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Richard S. Ehrlich is a Bangkok-based American foreign correspondent reporting from Asia since 1978, and winner of Columbia University's Foreign Correspondents' Award. Excerpts from his two new nonfiction books, "Rituals. Killers. Wars. & Sex. -- Tibet, India, Nepal, Laos, Vietnam, Afghanistan, Sri Lanka & New York" and "Apocalyptic Tribes, Smugglers & Freaks" are available at
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