Eighteen years ago, al-Qaeda operatives hijacked planes, toppled buildings, terrified an entire nation, and killed nearly 3,000 innocents. That the elaborate 9/11 plot went undetected will forever be remembered as one of the intelligence community’s worst failures. For many U.S. intelligence officials, memories of that day remain fresh, searing, and personal. Still hanging over the entrance to the CIA’s Counterterrorism Center is a sign that reads, “Today is September 12, 2001.” It’s a daily reminder of the agency’s determination to prevent future attacks—but also of the horrifying costs when intelligence agencies adapt too slowly to emerging threats.

For a decade after the Soviet Union’s collapse, the CIA and the FBI were mired in Cold War structures, priorities, processes, and cultures even as the danger of terrorism grew. My research has shown that even though many inside and outside U.S. intelligence agencies saw the terrorist threat coming and pressed for change years earlier, they could not get the necessary reforms enacted. The shock of 9/11 finally forced a reckoning—one that led to a string of counterterrorism successes, from foiled plots to the operation against Osama bin Laden. But now, nearly two decades later, America’s 17 intelligence agencies need to reinvent themselves once more, this time in response to an unprecedented number of breakthrough technologies that are transforming societies, politics, commerce, and the very nature of international conflict.

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