What if the U.S. could fight only one war at a time?

There is plenty of serious thinking behind this shift. The new strategy is meant to signal unambiguously — to allies, competitors and the Pentagon bureaucracy — that the U.S. is now focusing squarely on great-power competition and the immense challenges it presents for a force that has been preoccupied with counterterrorism and counterinsurgency for nearly two decades. It recognizes that America’s military advantages vis-a-vis China and Russia have eroded gravely, and that the Defense Department will need new high-tech capabilities and creative operational concepts to defeat either country should war break out.

The new strategy therefore puts a priority on getting right those key concepts and capabilities — which are mostly still nascent — over expanding the force by acquiring more aircraft carriers, Cold War-era fighter jets and other legacy capabilities that would simply get chewed up in a fight against Moscow or Beijing. And it is meant to wrench the Pentagon away from America’s old way of war — one that relied on assembling overwhelming power in a theater and then launching the war at a time of our choosing — and toward a new way of war in which U.S. forces will have to deny adversaries the ability to seize key terrain quickly, while operating in an incredibly deadly environment.

In sum, the Pentagon’s approach is based on the idea that the U.S. has to nail down how to defeat just one great power rival before it takes on anything more ambitious than that. This is a sensible approach, but one that also entails real risks in war and peace alike.