At the main operations room inside the National Counterterrorism Center, the flow of incoming data never stops. Analysts from across the government sit in front of their blinking computers, all facing huge TV screens tuned to news channels.
"On a daily basis, 10,000 reports come across our ops center and eyes are put on every one of those," said Russ Travers, deputy director of the center, who has been here, on and off, since it was established 16 years ago.
"There are in the neighborhood of 16,000 names within those pieces of information. We have to process all of that," he added.
The U.S. fight against terrorism is at a key juncture. More than 17 years after the 2001 attacks by al-Qaida, that group is no longer the force it was. And the Islamic State has lost its core territory.
Despite these U.S. successes, a host of evolving threats remain. So what should the U.S. effort look like going forward?
As someone who began his intelligence career in the Army 40 years ago, Travers is instinctively cautious.
"After 9/11, we talked about this being a generational struggle. I still very much believe that's the case," he said.
Over this past generation, the U.S. has sent many troops abroad and built a massive infrastructure at home to combat terrorism. Some are now calling for a reassessment, including President Trump, who says it is time to bring troops home from Afghanistan and Syria.
A safer country
Analyst Peter Bergen, of the New America think tank, acknowledges the price tag has been high, some parts of the system are redundant, and results have been uneven. But he says the U.S. is a safer place today.
"On 9/11 they were 16 people on the no-fly list. Now they are 81,000. On 9/11, there was no [Transportation Security Administration]. Annoying as you might find the TSA, that is a pretty big deterrent," he said.
He understands the temptation to remove troops from long-running conflicts, but says that brings risks of its own.
"We've already run this videotape in multiple different ways, which is if the United States is absent in these weak states, they can turn into failing states" vulnerable to terrorist groups, he said.
The more successful U.S. military actions over the past two decades have usually involved "a relatively small [U.S.] Special Operations footprint, where these groups work with local forces," he added.
A critical lesson from the 2001 al-Qaida attacks was the failure to see the looming threat and connect the dots. The Counterterrorism Center is the place built to do precisely that.
You don't often hear about the center in McLean, Va., but it's the place that pulls together disparate information from around the globe to give a comprehensive picture of potential risks.
It was designed for collaboration. The CIA, the FBI, the National Security Agency and even local police departments all have officers here to check and cross-check data coming from U.S. intelligence agencies, American embassies, foreign allies and open sources.
Every 12 hours, the center puts out a situation report on potential threats that's shared across the national security community.
"Terrorism information is unlike anything I've ever seen. It's always ambiguous. It's invariably incomplete. It's often completely bogus," Travers said. "But we have to make a determination about what do we follow, what don't we follow."
The U.S. has not been hit by a major terror attack from abroad since 2001. That's one reason the U.S. is shifting its security focus to great power rivalries, like those with China and Russia, and away from counterterrorism.
Yet challenges remain, like countering the radical Islamist ideology that keeps attracting new recruits.
"We know that the most authentic voices to stop a young person from joining a group like ISIS are those people who have already been there and have come back," said Farah Pandith, who was in charge of outreach to Muslim countries under President Barack Obama and is the author of a new book, How We Win.
The U.S., she said, needs to tap into its marketing skills and create campaigns
"available for young kids in a way that is savvy, is peer-friendly, that makes sense for them."
The counterterrorism center was built at a time when the country was focused on foreign threats. This is baked into the center's founding, where it is described as "the primary organization in the United States government for analyzing and integrating information pertaining to international terrorism."
Yet homegrown extremists have carried out most attacks in recent years, many by the far-right and white nationalists.
The FBI has the main responsibility for dealing with domestic extremism, and Travers described his center's role on this issue as "supporting the broader U.S. government effort."
He said the U.S. must adapt to a host of evolving threats, but he also offered this assessment: "We need to keep terrorism as a risk in perspective. It is not, it never has been existential unless and until it causes us to change who we are as a people."
And that, he said, is entirely in our own hands.
Greg Myre is a national security correspondent. Follow him @gmyre1.