From the lush, foggy valleys of southwestern China, satellite images show the accelerating buildup of nuclear weapons in China, a force designed for a new era of superpower competition.
One such valley is known as Zitong in Sichuan Province, where engineers have been building new bunkers and walls. The new complex is densely packed with pipes, suggesting the facility handles highly hazardous materials.
Another valley contains a double-fenced facility called Pingtong, where experts believe China is making plutonium-packed nuclear warhead cores. The main structure, which houses the 360-foot-tall ventilation stack, has been refurbished in recent years with new vents and heat spreaders. Additional construction is underway next door.
Above the entrance to the Pingtong facility, Chinese leader Xi Jinping’s signature recommendation is displayed in letters large enough to be visible from space. “Stay true to our founding cause and always remember our mission.”
These are one of several secret nuclear-related sites in Sichuan province that have undergone expansion and upgrades in recent years.
China’s military buildup is complicating efforts to revive global arms control after the last remaining nuclear arms treaty between the United States and Russia expires. Washington insists any subsequent agreement must also bind China, but China has shown no interest.
“The changes we see at these sites are consistent with China’s broader goal of becoming a global superpower. Nuclear weapons are an essential part of that goal,” said Renny Babiarz, a geospatial intelligence expert who analyzed satellite images and other visual evidence from the sites and shared his findings with The New York Times.
He likened each nuclear facility across China to a mosaic that shows a pattern of rapid growth when viewed as a whole. “There has been an evolution across all of these sites, but broadly speaking the change has accelerated since 2019,” he said.
Tensions with the United States are increasing due to China’s nuclear expansion. Thomas G. DiNanno, the U.S. Undersecretary of State for Arms Control and International Security, publicly accused China this month of secretly conducting “nuclear explosive tests” in violation of a global moratorium. The Chinese government has rejected the claims as untrue, and experts have debated how strong the evidence for Mr. DiNanno’s claims is.
China will have more than 600 nuclear warheads by the end of 2024 and 1,000 by 2030, according to the Pentagon’s latest annual estimates. China’s stockpile is far smaller than the thousands held by the United States and Russia, but the growth is still troubling, said Matthew Sharp, a former State Department official who is now a senior fellow at MIT’s Center for Nuclear Security Policy.
“I think it’s really hard to say where it’s going without real dialogue on these topics, which we’re lacking, and that’s dangerous to me, because now we have to respond and plan for the worst-case interpretation of the relevant trend lines,” he said.
The Sichuan site was built 60 years ago as part of Mao Zedong’s ‘Third Front’ project. This project was to protect China’s nuclear weapons production laboratories and factories from attacks by the United States or the Soviet Union.
Tens of thousands of scientists, engineers and workers secretly worked to carve out the mountainous interior, what he called an “inland nuclear empire” in a book co-authored by Danny B. Stillman, an American nuclear scientist who visited the region.
As tensions between China, the United States, and Moscow subsided in the 1980s, many “third front” nuclear facilities were closed or scaled back, often relocating their scientists to new weapons laboratories in the nearby city of Mianyang. Sites such as Pingtong and Zitong continued to operate, but changes in subsequent years were piecemeal, reflecting China’s policy at the time to maintain a relatively small nuclear arsenal, Dr. Babiarz said.
That era of restraint disappeared about seven years ago. China has rapidly begun building or upgrading many nuclear weapons facilities, and construction at sites in Sichuan has also accelerated, Dr. Babiarz said. The build includes a large-scale laser ignition laboratory at Mianyang that can be used to study nuclear warheads without detonating an actual weapon.
According to Dr. Babiarz, the design of the Pingtong complex suggests it is being used to create pits for nuclear warheads, usually metal cores containing plutonium. He noted that the architecture is similar to that of pit manufacturing facilities in other countries, including Los Alamos National Laboratory in the United States.
New bunkers and ramparts at Zitong are likely to be used to test “high explosives,” referring to chemical compounds that explode to create conditions for a chain reaction of nuclear materials, experts say.
“There is a layer of high-yield explosives and at the same time a shock wave ruptures into the center. We need explosive tests to perfect this,” said Hui Zhang, a physicist who studies China’s nuclear program at Harvard University’s Kennedy School of Medicine, who investigated Dr. Babiarz’s findings.
The complex includes an oval-shaped area the size of 10 basketball courts.
The exact purpose of these upgrades is still a matter of debate. Dr. Zhang said satellite images alone provide limited information. “We don’t know how many warheads have been produced, but we are only looking at factory expansion,” he said.
Some of the recent changes may simply reflect upgrades for safety, said Dr. Zhang, author of the new book The Untold Story of China’s Nuclear Weapon Development and Testing. He said Chinese nuclear engineers may need more facilities and test sites at Zitong to modify warhead designs for new weapons such as submarine-launched missiles.
One of Washington’s main concerns is how this larger, more modern arsenal could change China’s behavior in times of crisis, especially on the Taiwan issue.
China wants to be “in a position where it believes it is largely immune from U.S. nuclear coercion,” said Michael S. Chase, a former U.S. assistant secretary of defense and now a senior political scientist at RAND. “Perhaps they will decide that it could have an impact on the conventional conflict over Taiwan.”
Note: Research on the site conducted by Renny Babiarz’s company, AllSource Analysis, was funded by two organizations: the Open Nuclear Network and the Center for Verification Research, Education, and Information. This institution has received support for its work from the Government of Canada. The New York Times obtained additional satellite images of its own of the site and shared them and Dr. Babiarz’s report with other nuclear weapons experts for evaluation.
Top image source: Satellite images from Airbus, September 9, 2022 and February 5, 2026
