There is less trust between Washington and Beijing than at any point since 1979

WHEN CONDUCTING war games between China and America, David Ochmanek of RAND Corporation, a think-tank, worries most about an invasion of Taiwan, the security of which is implicitly guaranteed by America. In one scenario the red team unleashes a “joint firepower strike” on Taiwan’s defence forces and on American forces, bases and command-and-control nodes in the Pacific, including on Okinawa and Guam. Many of the blue team’s planes are destroyed on the ground, and its runways disabled. China severs communication links as part of an effort to gain information superiority, part of a full-spectrum strategy called “system-destruction warfare”. Then comes the amphibious assault on the island. American submarines knock out some portion of the invasion force with torpedoes, but surface-level carriers and frigates are hammered by Chinese anti-ship missiles if they venture near the fight. “We always assume that the United States intervenes forcefully and early,” Mr Ochmanek says. But now, in contrast to years past, “I would not have confidence that we would succeed.”

The probability of such a world-changing military conflict between the two countries remains mercifully low. But it is becoming something to ponder beyond simulations, a reflection of how grim their relationship has become. Lesser conflicts may be reignited this year—over trade,...