It is estimated that there are nearly 750,000 miles of internet cables lying across the ocean floor, long threads of silica, surrounded by copper and plastic, that connect the world’s continents to each other at two-thirds the speed of light. But of course information can always travel faster. So last year one of America’s telecom companies installed a secret new technology to improve its underwater infrastructure. Soon after the update was completed, however, the telecom made a terrifying discovery. A Chinese competitor had apparently re-created the technology, even improving on the original design, and was about to start installing it off the coast of China. The telecom assumed there had been a spy in their midst, and brought in a team of investigators to find out who was responsible.

The investigators performed the usual digital forensics, running background checks on employees with access to the labs, checking data logs to see if hackers had breached the company’s servers, and so on. As it turned out, however, the heist had been old-school. According to one of the investigators on the team, the Chinese simply dispatched deep-sea divers to locate a piece of this new hardware, go down to the bottom of the ocean and grab it.

Foreign espionage has long been an underreported fact of life in Silicon Valley. Stealing intellectual property, after all, is much easier than creating it yourself. Apple, for example, took a decade or more to develop the touchscreen technology that went into the first iPhone; Chinese companies copied it all in a matter of years. (Plenty of people would have trouble distinguishing a real iPhone from a Chinese “clone,” just as they would struggle to find the differences between a real Louis Vuitton bag and a knockoff.) As clumsy and impolitic as Donald Trump’s trade war is, he’s not wrong that China has taken advantage of American innovation.

More recently, however, the technological cold war between Beijing and Washington has reached a boil over one technology in particular: 5G, a next-generation cellular network technology that promises speeds 100 times faster than your current smartphone plan. With download speeds like that, it’ll be easier than ever to build smart homes and smart cities. Practically any internet-connected device will become a potential supercomputer. And then there are the use cases that we can only begin to imagine: remote surgery, fully self-driving cars, augmented-reality eyeglasses far beyond our current capabilities.

Security experts I’ve spoken with warn that while China started off at a disadvantage in 5G development, years of industrial espionage have allowed them to leapfrog the United States. Now China—or, more specifically, the Chinese telecom Huawei—is hoping to build 5G mobile-phone networks all over the world, including in the United Kingdom, which along with the U.S. is part of the so-called Five Eyes intelligence-sharing alliance. The fear is that, by providing the infrastructure for the world’s next great telecommunications network, the Chinese government will be able to spy on, well, just about everyone. It would be as if the Chinese had a listening device in every corner of America: every home, business, traffic camera, research and development lab, and cubicle from Silicon Valley to Washington, D.C. In such a scenario there would be no need for deep-sea divers to swim to the bottom of the ocean to steal intellectual property. They would simply capture the information as it flowed along their own pipes.

Maybe all this sounds a tad dramatic, but history is full of terrifying examples of what happens when technological arms races spiral out of control. Even before the end of World War II, the testy alliance between the U.S. and USSR collapsed into a cold war for nuclear supremacy. It had all started years earlier, when advancements in nuclear fission gave way to nuclear bombs, which set the stage for a battle that could be started by any side, but where all of humanity would inevitably lose. What’s so interesting, looking back on that time period, is that the Russians developed their own nuclear technology thanks in large part to the Americans. As is detailed in the book Midnight in Chernobyl: The Untold Story of the World’s Greatest Nuclear Disaster, written by Adam Higginbotham, Russia was able to advance its nuclear capabilities by some well-placed spies in U.S. research and development labs, and by reading a best-selling book, titled, Atomic Energy for Military Purposes, which had been published by none other than the United States government.