Massive U.S. airstrikes on Islamic State militants in Syria are meant partly as a message to the group and a move to ensure that the insurgents don’t try to take advantage of the chaos following the overthrow of President Bashar Assad’s government.

The speedy Taliban takeover of Afghanistan has revived alarms about a resurgent al-Qaida and new terrorism threats against the U.S. The group's danger to the United States had been eclipsed in the past two decades by other threats, but experts are concerned that al-Qaida could again be given unfettered safe harbor by the Taliban.