Seventeen years ago today, nineteen radical Islamist terrorists caught the US flat-footed and murdered almost 3,000 people in attacks on New York City and Washington DC. In the aftermath of the al-Qaeda attack, we discovered all the ways in which our national-defense strategy had not kept up with a changing world. In the wake of the Cold War, the US had never really recalculated for defenses against asymmetrical threats and failed to take those seriously, even after the first attack on the World Trade Center in 1993.

Have we learned our lessons? FBI director Christopher Wray tells CBS This Morning that our intel and security apparatuses have adapted to the new threats — and that those defenses are constantly being tested:

.@FBI director Christopher Wray on the threat to the United States: "Today's terrorism threat is everywhere, coast to coast, north, south, east, west." pic.twitter.com/RhnBGDYy6d

— Norah O'Donnell 🇺🇸 (@NorahODonnell) September 11, 2018

Q – Can you say how many terrorist attacks you've thwarted in the past year? @FBI Director Wray: "We had about 1,000 investigations into just these homegrown violent extremists. That's out of about 5,000 terror investigations." pic.twitter.com/S2dTBzbmHH

— Norah O'Donnell 🇺🇸 (@NorahODonnell) September 11, 2018

NORAH O’DONNELL: Do you think another 9/11-style attack could happen today?

CHRISTOPHER WRAY: Well, I would say this, we are dramatically better positioned, the FBI is a totally different kind of organization in a lot of ways. …

O’DONNELL: Can you say how many terrorist attacks you’ve thwarted in the past year?

WRAY: In the last year, or so, we’ve thwarted attacks in San Francisco on the pier. … We’ve prevented an attack in a shopping mall in Miami… We prevented an attack in Cleveland, on the July Fourth holidays, where… there would have been thousands of people to celebrate our freedom. … We had about 1,000 investigations into just these homegrown violent extremists. That’s out of about 5,000 terrorism investigations.

O’DONNELL: Right, that doesn’t even include the ISIS or al Qaeda-related.

WRAY: Doesn’t include ISIS, doesn’t include al Qaeda, it doesn’t include domestic terrorism even. … This is a significant issue. We had about 120 arrests, terrorism-related arrests, last year alone. That’s just in the arrest context. So there’s a lot happening every day, 365 days a year right now in the terrorism front.

This shows how the threat has changed since 9/11, too. Al-Qaeda and others have tried large, systemic attacks on the US since 9/11, but those have all failed. The follow-on attacks on passenger aviation failed, and both the Shoe Bomber and Underwear Bomber were thwarted by passengers who have become aware of the suicidal-attack threat. Attempts to blow up cargo planes got exposed before it could do any damage; its mastermind was recently killed in our forward strategy against terror networks.

Instead, the focus has shifted to grassroots radicalization and terror action on smaller scales. Around the world, recruits go on stabbing sprees and car attacks, including in the US, where the body counts are lower but the return on investment in terms of terror caused remains high. Massacres like the Pulse nightclub shooting in Orlando and the Fort Hood shooting exacerbate both cultural and political tensions. Some of those get stopped ahead of time, thanks in part to a populace that learned to speak up after 9/11, but others succeed thanks to their lack of visibility and overt coordination. We’re still in a constant war on terror, but at a lower pitch.

So far, the FBI and other counterterrorist agencies have done a pretty good job of fighting the current war, as much as it can be fought on the defense side. The problem will be whether they can anticipate the next war, which was the failure that led us to 9/11– a failure to imagine, to anticipate the next iteration and the next threat. Few (other than perhaps Tom Clancy in 1994’s Debt of Honor) anticipated the use of passenger aircraft as suicidal guided missiles for terror operations. Until 9/11, that is, when it became an obvious issue in retrospect, and we hardened flight decks to belatedly deal with the vulnerabilities.

What failures of imagination might we suffer from today? Do we even know what we don’t know, our unknown unknowns, as Donald Rumsfeld once famously postulated? That’s one lesson from 9/11 that should constantly be in the back of our minds — whether we have closed the imagination gap.