Since Russia invaded Ukraine, Prime Minister Fumio Kishida has insisted that security is indivisible and that “Ukraine today may be East Asia tomorrow.”

That logic was evident throughout last week’s Group of Seven leaders summit (and the entire G7 process that has unfolded over the last year). The time and attention given to China in the discussions and the documents is proof that Kishida’s thinking and concerns are shared throughout the world.

Implicit in the indivisibility argument is an inference that governments need not choose between theaters in the case of simultaneous crises. Elbridge Colby argues that sort of thinking is, for the United States at least, “a dangerous delusion.” His analysis has triggered a noisy and important debate in Washington and allied capitals about U.S. priorities and their implications.