The rivalry between the United States and China over artificial intelligence is often described as a contest of speed and ingenuity. Commentators count patents, compare benchmarks, and track investment flows.

The United States put a price on national security and called it a fee. A 15 percent export duty was floated on shipments of technology that had been banned months earlier. At the same time, officials threatened sweeping tariffs on semiconductors, on goods that contain them, and even on the tools that make chips; and they reopened sales of Nvidia’s H20 to China in the midst of tense bargaining over rare earths. Reports that summer described these moves in detail, showing how controls—once insulated from bargaining—were folded into trade talks. In a matter of months, national-security rules had become negotiable.