American companies are world leaders in technology—be it innovative software, cloud services, artificial intelligence, or cybersecurity products. Yet beginning as many as three years ago, hackers believed to be backed by the Chinese government did something the United States, the tech powerhouse, could not adequately defend against: they gained and maintained access to major U.S. telecommunications networks, copying conversations and building the ability to track the movements of U.S. intelligence officers and law enforcement agents across the country. The attack, dubbed “Salt Typhoon,” constituted a large part of a global campaign against telecoms, and it penetrated systems at many U.S. carriers so thoroughly that officials will almost certainly never know the full scope of the capabilities China achieved to spy on Americans’ communications.

Salt Typhoon was more than a one-off intelligence success for China. It reflected a deeper, troubling reality. Mere decades after the widespread adoption of the Internet opened a new realm of geopolitical contestation, China is positioning itself to dominate the digital battle space. The United States has fallen behind, failing to secure a vast digital home front—and the physical assets that depend on it. Because cyberspace has no borders, the U.S. homeland is always in the fight. Every hospital, power grid, pipeline, water treatment plant, and telecommunications system is on the frontlines, and most of the United States’ critical infrastructure is unready for battle.

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