President Trump has just pushed the plunger on a sequence of crises.

The first will be a crisis with allies and other partners. Will they agree to reimpose their sanctions on Iran? It’s not just NATO countries that will have to be cajoled or coerced. Complying with UN-voted sanctions, India reduced its dependence on Iranian crude oil from 13 percent of its imports in 2009–2010 to 5 percent in 2014–2015. Iran, the second-largest oil supplier to the world’s third-biggest oil importer before the sanctions hit, is rapidly recovering its market share—and India plans to double its imports in the coming year. What’s the plan for getting India back on board?

China has emerged as Iran’s largest trading partner. Its trade with Iran jumped 30 percent in the first six months of 2017. China has extended credits to Iran totaling some $35 billion, a significant sum for the shaky Iranian economy. Who will make China stop?