Israeli forces shot and killed four Palestinian militants near the Gaza border fence after one tossed a hand grenade at Israeli troops on Saturday, the military said.

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.