During his first term as president, Donald Trump saw the height of a violent civil war in Syria, a resurgence of Islamic State activity, and a rise in ISIS-inspired attacks both abroad and on U.S. soil. Eight years later, many of these bogeymen have returned. In the last eight weeks, Syrian rebels launched a lightning offensive, wresting back control of the country and then of its capital—forcing longtime...

A pair of suspected terrorist attacks on New Year’s Day were both allegedly carried out by former U.S. service members, raising questions about how those with access to sensitive intelligence and the nation’s most advanced weapons get swept up in radical beliefs.  Early Wednesday morning, Texas resident Shamsud-Din Jabbar allegedly plowed into a crowd on Bourbon Street in New Orleans, killing 14. He was a former Army staff sergeant, with...