This month’s closure of embassies for more than a week was, in part, a response. The State Department said the action was taken “out of an abundance of caution.”

But working diplomats worry that if embassies close in response to every threat, their work will be impossible.

“Washington makes decisions on a zero-risk basis, [but] there has been a level of risk for years,” noted Ronald E. Neumann, a former U.S. ambassador to Afghanistan.

Put more bluntly: If a bomb maker in Yemen can close U.S. embassies just by making plans for his next attempt, doesn’t that mean the terrorists have won?

Over the long run, diplomats are going to have to find new ways to work without exposing themselves to danger, according to the State Department’s former counterterrorism chief.