Espionage and counterespionage have been essential tools of statecraft for centuries, of course, and U.S. and Chinese intelligence agencies have been battling one another for decades. But what these recent cases suggest is that the intelligence war is escalating—that China has increased both the scope and the sophistication of its efforts to steal secrets from the U.S. “The fact that we have caught three at the same time is telling of how focused China is on the U.S.,” John Demers, the head of the National Security Division at the Justice Department, which brought the charges against Mallory, Hansen, and Lee, told me. “If you think about what it takes to co-opt three people, you start to appreciate the actual extent of their efforts. There may be people we haven’t caught, and then you have to acknowledge that probably a small percentage of the people who’ve been approached ever go as far as these three did.”

Many espionage cases don’t go public. “Some of the cases rarely see the light of a courtroom, because there’s classified material we’re not willing to risk,” one U.S. intelligence official told me, speaking on condition of anonymity due to the sensitivity of the topic. “Sometimes they’re not charged at all and are handled through other means. And there are others that remain ongoing that have not and will not become public.”

These recent cases provide just a small glimpse of the growing intelligence war that is playing out in the shadows of the U.S.-China struggle for global dominance, and of the aggressiveness and skillfulness with which China is waging it. As China advances economically and technologically, its spy services are keeping pace: Their intelligence officers are more sophisticated, the tools at their disposal are more powerful, and they are engaged in what appears to be an intensifying array of espionage operations that have their American counterparts on the defensive. China’s efforts aimed at former U.S. intelligence officers are just one part of a Chinese campaign that U.S. officials say also includes cyberattacks against U.S. government databases and companies, stealing trade secrets from the private sector, using venture-capital investment to acquire sensitive technology, and targeting universities and research institutions.