On the morning of September 11, 2001, nineteen men with box cutters hijacked four commercial airliners on the US East Coast within roughly half an hour of one another. Two were flown into the towers of the World Trade Center in Manhattan, which collapsed inside two hours; one struck the Pentagon; the fourth, United 93, crashed in a Pennsylvania field after passengers stormed the cockpit. Roughly 3,000 people from over ninety countries were killed — the deadliest attack on American soil. The plot was conceived by al-Qaeda in the caves and compounds of Taliban-ruled Afghanistan, financed through informal Gulf money networks, and executed by a mostly Saudi cell that had spent the previous year inside American flight schools and rental apartments. The asymmetry of inputs to outputs — a few hundred thousand dollars against trillions in response — has never been matched in the history of strategic violence.
The American response defined the next two decades. Within weeks a US-led coalition invaded Afghanistan to topple the Taliban regime that had sheltered Osama bin Laden; that war lasted twenty years and ended in August 2021 with a chaotic withdrawal from Kabul and the Taliban back in power, the original objective effectively reversed. In 2003, on disputed and partly fabricated intelligence about weapons of mass destruction, the United States invaded Iraq, deposed Saddam Hussein, and triggered a regional unraveling — insurgency, civil war, and ultimately the emergence of ISIS, the Syrian catastrophe, and a refugee crisis that helped destabilize European politics. At home, the Patriot Act, NSA mass surveillance, Guantánamo detention, CIA black sites, drone-strike assassination, and 'enhanced interrogation' — all politically inconceivable on September 10, 2001 — became routine instruments of the post-9/11 state, normalizing executive power that long outlasted the emergency. Estimated US spending on the 'War on Terror' exceeds eight trillion dollars; estimated direct and indirect deaths in the wars it triggered run to roughly four hundred thousand civilians and well over a million total. The deepest cost may be civic: a generation of American adulthood spent at war, and a corrosion of trust in the official case for it.
The strategic distraction of the War on Terror is now widely read, in Washington as much as in Beijing, as the period during which the United States failed to notice China's rise — the years it spent counting insurgents in Anbar while Shenzhen built the supply chains of the next century. The opportunity cost — what the U.S. did not do in those two decades, while it was preoccupied with the Greater Middle East — is the largest line item in any honest accounting of the unipolar moment. Every current debate about the limits of American power, the cost of forever wars, and the surveillance state runs back to that one September morning.