AUDIE CORNISH, HOST:
The U.S. embassy in Yemen reopened this week. All 19 U.S. missions had closed two weeks ago in response to a terror alert. But they're back in business now and no terror attack ever came. This turn of events, however, raises questions about how real the threat was and whether the alert was justified. To find out when and why warnings are issued, NPR's Tom Gjelten turned to those in the know, members of the intelligence community.
TOM GJELTEN, BYLINE: The government certainly got the public's attention when it said it had learned of a specific terror threat, one of the most serious since 9/11. But then nothing happened. Intelligence officials insist that just because there wasn't an attack, doesn't mean the threat wasn't real. It may be the threat lessened because of what the United States did.
And with the danger diminished, the Obama administration decided it was safe for diplomats to go back to work. Matthew Olsen directs the National Counterterrorism Center.
MATTHEW OLSEN: We've been monitoring the situation over the last couple weeks and based on all of the activities that we undertook to share this information, to harden our defenses, to take some actions in Yemen.
GJELTEN: Drone strikes, for example, against suspected al-Qaida operatives there.
OLSEN: All of that activity helped to mitigate the threat and so that led to the ability to open up those embassies.
GJELTEN: So was it really necessary to publicize that terror threat two weeks ago? Skeptics noted that the alert diverted attention from the uproar over government surveillance of American's phone and email records. Whether and when to warn has long been debated within the intelligence community. It's expensive to mobilize security forces. Closing missions is also costly in time, money and political standing. Terror groups might be tempted to bluff that they're going to attack, just to see the reaction. Matthew Olsen says intelligence agencies consider those downsides before issuing a terror alert.
OLSEN: Will that particular action be something that we would prefer not to take in order to not let our adversaries know that we've got the ability to see what they're doing or understand what they're doing? But again, at the end of the day, we've got to protect the American people. We have to protect our embassies and we have to share that information with other countries. And we have a duty to warn.
GJELTEN: Warning is actually a specialty within the intelligence profession. There are formulas to help officials decide whether to issue warnings and what to say. Charles Allen, for six years in the early '90s, was the designated national intelligence officer for warning.
CHARLES ALLEN: Always a risk management decision. It takes a lot of thought to do it right. You have to make a decision very quickly as to whether to get the public involved. You do want to protect how this information is accessed and our track record there is not so good, frankly.
GJELTEN: Not so good because sometimes officials reveal too much about what they're worried about. On the other hand, the CIA and the Obama administration was harshly criticized for not calling enough attention to the terrorist threat in Libya before the mission in Benghazi was attacked last September. The National Counterterrorism Center is the U.S. government headquarters for keeping track of those threats and director Olsen says the Benghazi experience has made the government more aware of, in his words, the duty to warn.
OLSEN: We're trying to learn all the time from what's worked and what hasn't worked. And certainly since Benghazi, we've been very focused on are we doing everything we can to make sure that the information we see is provided to those embassies, to our consulates, to our personnel around the world.
GJELTEN: The most recent terror threat was issued after U.S. intelligence agencies intercepted communications that suggested an attack was being planned. It's possible the response to that threat helped divert an attack for now. But Matthew Olsen says the threat has not passed.
OLSEN: It was a serious and credible threat that I think all of us in the counterterrorism community decided was something that we needed to take very seriously. There hasn't been any action that we've seen, but there still is a threat in that region to U.S. persons so we're still monitoring that situation very carefully.
GJELTEN: With the anniversary of the 9/11 attacks less than three weeks away, attention to the terror threat is bound to increase again, but every time an alert is issued and no attack follows, there is a danger that the American public, other governments, perhaps even the whole national security establishment will begin to let down their guard. Tom Gjelten, NPR News, Washington. Transcript provided by NPR, Copyright NPR.