On the twenty-fifth anniversary of Pearl Harbor in 1966, President Lyndon Johnson proclaimed December 7 a national day of commemoration, calling on Americans to remember those killed and the sacrifices that followed. For most Americans today, September 11 has become the nation’s defining day of remembrance and mourning.
I could easily use this solemn anniversary to measure the state of American national security under the current administration. But another column about Donald Trump’s dismantling of our military and intelligence capabilities and the politicalization of counterterrorism priorities would shift the focus onto someone who does not deserve our attention on this day.
Instead, I want to consider a fact often noted on this anniversary: Our nation has not suffered anything resembling the attacks of September 11 since. Terrorism scholar Bruce Hoffman recently called the absence of another attack on the scale of 9/11 a “towering achievement” — a success of post-9/11 reforms.
That counterterrorism achievement should be celebrated. In the years following the attacks, the United States has disrupted terrorist organizations and corrected serious national security weaknesses that the attacks revealed.
But September 11 was more than a terrorist attack. It was a strategic surprise. By that measure, the record is less reassuring. Pearl Harbor had not been repeated in the six decades before 2001, either.
Strategic surprise rarely returns on the same path or bearing the same signposts. It comes from another direction and under different circumstances, exploiting assumptions that seemed reasonable until they didn’t.
Strategic surprise does not repeat itself — it rhymes, to borrow the aphorism attributed to Mark Twain.
That is why the anniversary should inspire not just remembrance — and more than guarded satisfaction that nothing like it has happened again. It should remind us how quickly the lessons of one failure can become the assumptions of the next. The farther we move from catastrophe, the greater the temptation to believe that the systems built in response to it have made us safer from strategic surprise itself.
The reforms after September 11 addressed indisputable failures. The 9/11 Commission concluded that intelligence agencies had not shared information effectively, lacked flexible and interconnected collection processes to address gaps, and failed to imagine that an adversary might use familiar tools in an unfamiliar way. Subsequently, the intelligence community changed. Information moved more freely. Counterterrorism became an integrated mission. Watchlisting was refined. Aviation security was improved.
But governments tend to prepare for the last war. They fix the vulnerabilities they now understand, while the next adversary looks for a different way in.
Israel offers a sobering example. It spent fifty years studying the intelligence failure surrounding the 1973 Yom Kippur War, yet Hamas still achieved strategic surprise in October 2023. Israeli intelligence in 1973 did not believe Egypt and Syria would choose to attack. Fifty years later, it again judged that its Hamas adversary would not choose war, believing that it had become more interested in preserving its rule over Gaza and the existing status quo than in risking everything on a major attack that could not plausibly defeat Israel or destroy its armed forces. Such an attack could inflict enormous bloodshed and provoke a devastating Israeli response.
That is why I find myself also looking at the anniversary through a second lens: not simply at what we have prevented but also at whether the lessons of that success might leave us less alert to a strategic surprise that takes another form. The system built afterward unquestionably made certain kinds of attacks harder and gave the United States capabilities it lacked in 2001. But better collection and information sharing cannot eliminate the danger that institutions will interpret new evidence through assumptions that have become too comfortable to question.
Assumptions have a longer life than the circumstances that produced them. The intelligence and national security system today’s young Americans are inheriting was shaped by an attack that occurred before they were born. Much of what was built after September 11 remains essential. But some of the assumptions embedded in that system — that the next mass-casualty threat will look like the last one, that the terrorism architecture built for 2001 is still the right filter for 2026 — may no longer fit the threats they will face. The harder task for today’s young Americans will be knowing the difference.
For them, September 11 is history, as Pearl Harbor was to me. By the time I graduated from high school, I knew what had happened on December 7 and why it mattered. And I inherited a national security system shaped in its aftermath — one built for a different kind of threat entirely: the Soviet Union and nuclear-armed missiles that could strike with little warning.
That system was reformed once already, imperfectly, when it collided with September 11.
Today’s young Americans stand at a similar distance from September 11. They did not experience the attacks, but they are inheriting institutions, priorities, and assumptions built in response to them. The question is not whether those lessons should be forgotten. It is whether we can distinguish the lessons that remain essential from the assumptions that belong to the world of 2001.
For many of them, the pandemic may prove to be the defining event of their generation. They have also come of age amid wars abroad, rapid technological change, and political upheaval at home. Their national security problems will not be the same as ours, just as ours were not those of the generation shaped by Pearl Harbor.
The generation now entering the public and private sector should not be asked merely to preserve the institutions, assumptions, and strategies created after 9/11. It should be encouraged to question them with the same seriousness with which an earlier generation questioned what had failed on September 11.
That generation should inherit the lessons of the past but not be bound by the world that produced them.
Brian O’Neill, a retired senior executive from the CIA and National Counterterrorism Center, is an instructor on strategic intelligence at Georgia Tech. His Safehouse Briefing Substack looks at what’s ahead in global security, geopolitics, and national strategy.
