America built a fortress after 9/11. Then the threat started hiding in plain sight

On the morning of Sept. 11, 2001, Javed Ali drove past the Pentagon on his way to work in northern Virginia.

Roughly half an hour later, American Airlines Flight 77 slammed into the building.

From his office in Falls Church, Ali could see smoke rising from the Pentagon. A year later, in a turn that captured how dramatically the country had changed, he was walking into the still-damaged building himself — now working in the Defense Intelligence Agency's counterterrorism office.

"It was a very eerie and odd and surreal moment in my career," Ali told Fox News Digital.

Ali's career would eventually take him from the DIA to the newly created Department of Homeland Security and later the FBI, giving him a front-row seat to the enormous national security architecture America constructed after the deadliest foreign attack on U.S. soil.

Twenty-five years later, that architecture presents something of a paradox.

By one of its clearest measures, the post-9/11 system appears to have made another attack on the scale of 9/11 far harder. The United States has not suffered another terrorist attack remotely approaching the scale and complexity of 9/11, which killed 2,977 people. U.S. intelligence and military operations dismantled much of the al Qaeda network that planned it, while new agencies, surveillance authorities, watchlists and intelligence-sharing systems were designed to ensure that another group could not exploit the same seams in American defenses. The 2026 U.S. intelligence community assessment said counterterrorism operations have degraded al Qaeda and ISIS's ability to quickly rebuild their leadership and plan large-scale attacks against the U.S. homeland.

But success against the threat of 2001 did not eliminate terrorism. It helped change it.

Today's most difficult threats increasingly involve individuals radicalized online, small cells with little warning signature, foreign terrorist organizations seeking to inspire attacks from afar, and an expanding layer of cyber and state-sponsored threats capable of reaching deep inside the United States without hijacking an airplane.

The question 25 years after 9/11, therefore, is not simply whether Americans are safer.

They are safer from one kind of attack — while increasingly exposed to others.

The scale of the American response was extraordinary.

Just over two months after the attacks, President George W. Bush signed legislation creating the Transportation Security Administration. TSA says its creation amounted to the largest civilian undertaking in U.S. government history at the time, with the federal government rapidly assuming responsibility for airport passenger and baggage screening.

The following year, Congress created the Department of Homeland Security, combining all or part of 22 federal agencies and offices. DHS began operating in March 2003 and today employs more than 260,000 people across missions ranging from border and aviation security to cybersecurity, intelligence and emergency response.

The changes went far beyond new agencies.

TheIslamist terrorist groups to conduct "large-scale complex attacks" have pushed them toward information operations and propaganda designed to inspire or enable people in or with access to Western countries.

The assessment said there were at least three Islamist terrorist attacks in the United States in 2025 and that law enforcement disrupted at least 15 U.S.-based Islamist terrorist plotters that year. Roughly half of those disrupted plotters had some online contact with Islamist terrorists or were inspired by foreign terrorist organizations, according to the assessment.

The vulnerability was demonstrated on New Year's Day 2025, when critical infrastructure for espionage, financial gain and possible future disruption. It also warns that artificial intelligence is accelerating cyber capabilities and that several state adversaries are developing missile systems capable of threatening the homeland.

The security landscape that began with al Qaeda operatives training to fly passenger jets has therefore expanded into something far less geographically defined: terrorist propaganda transmitted to an individual's phone, malicious code inserted into a computer network, attacks on critical infrastructure and state adversaries capable of reaching Americans from thousands of miles away.

For Ali, however, the evolution of the threat should not lead Washington to conclude that the original threat has vanished.

One of the central lessons of the years before Sept. 11, he said, was that emerging terrorist organizations have to be confronted before they have the time and space to develop operational capability.

"When these terrorist threats start to emerge, whether it's overseas or here, you have to put pressure on them before they gather momentum to carry out operations," Ali said.

The danger, he argued, would be allowing counterterrorism to fall so far down Washington's list of priorities that the country begins recreating the complacency that existed before 9/11.

"Terrorism as a tactic is probably never going to be defeated," Ali said.

Twenty-five years after he watched smoke rise from the Pentagon, Ali's answer to whether America is safer reflects the contradiction at the heart of the post-9/11 era.

The United States built a massive system to prevent the next 9/11.

It appears to have made another 9/11 far harder to execute.

The harder question now is whether that system can recognize the attack that doesn't look anything like it.