For any aspiring Paul Revere sounding the alarm on nuclear nonproliferation, after more than a year of setbacks, the most promising news this month is four words: “The allies are coming.”

The visits of Japanese Prime Minister Shinzo Abe and French President Emmanuel Macron to the United States will shape developments in May on the two biggest nuclear issues on the world stage: North Korea and Iran. Their outcomes could influence whether President Trump takes the nation to war on either the Korean Peninsula, in the Middle East, or both.

Abe and Macron make their visits with unprecedented leverage. They start out knowing President Trump better than he knows his own new national security adviser. Both leaders can talk to Trump about the high stakes of policies towards North Korea and Iran, and convince him the United States is best off tethered to its allies.