Dhaka, March 7 -- US President Donald Trump has cast serious doubts on the future of the postwar international order. In recent speeches and United Nations votes, his administration has sided with Russia, an aggressor that launched a war of conquest against its peaceful neighbor, Ukraine. His tariff threats have raised questions about longstanding alliances and the future of the global trading system, and his withdrawal from the Paris climate agreement and the World Health Organization has undercut cooperation on transnational threats.

The prospect of a wholly disengaged, self-focused United States has troubling implications for world order. It is easy to imagine Russia taking advantage of the situation to try to dominate Europe through ...