Japan, Europe and the United States are the leading stakeholders in the liberal international order constructed after 1945 and consolidated after 1989. Together, the allies rebuilt a world ruined by war, defeated Soviet tyranny, sustained great-power peace in Asia, spurred a wave of democratic transitions, and catalyzed a global economic miracle.

But as these nations prepare to gather for the G7 summit in May, that liberal order is now fraying. China's leaders are deploying military force to redraw the strategic map of Asia. Russia's leader, instead of celebrating the liberation of his people from tyranny, sees the collapse of the Soviet system as a tragedy and is working to build a new shadow empire in Eurasia. Western democracies are under pressure at home from forces of nativism, populism, and protectionism that threaten historic gains from globalization.

In response to the steady erosion of the liberal international order, the U.S., Europe and Japan must cooperate more systematically to bolster a system that best protects their people's common interests. The alternative is a more fragmented and contested world, with powers that do not share the allies' core values shaping global politics at their expense. The need for trilateral cooperation among the world's principal market democracies is urgent, both to strengthen the rules-based order and to create a more accommodative international context in which to renew the foundations of governance and growth at home.