On the surface, white supremacists and Islamic State recruits would not seem to have much in common. One group embraces a racist, anti-immigrant ideology and is mobilized by fear that a majority of people in the United States will soon no longer be white.

In the 4½ months since U.S.-backed forces declared victory over the Islamic State terror group’s last shred of territory in Syria, there has been a steady drumbeat of doubt.

Iran has seized another oil tanker in the Persian Gulf — this one, it says, was smuggling oil to Arab nations — weeks after it detained a British-flagged tanker and attacked several others.