On this day, 25 years ago, the world changed forever. Eliot Wilson takes us through the tragic events that unfolded on September 11th 2001

They came out of a cloudless azure sky on a warm Tuesday morning in September. It could have been the backdrop for a film, dazzling colours and razor-sharp contrasts. CBS News diagnosed “ideal conditions for flying”.

At 8.46 am, American Airlines Flight 11, a Boeing 767-200ER with 92 people on board, crashed into the North Tower of the World Trade Center in Lower Manhattan. It struck between floors 93 and 97, occupied by Marsh McLennan: hundreds were killed instantly, including everyone on the aircraft and in its path. All 358 people at Marsh McLennan that day died. Those on the 13 floors above would burn alive, asphyxiate or choke. 200 jumped from the tower, knowing the fall was unsurvivable.

It was already the deadliest terrorist attack in American history, surpassing the death toll of 168 when anti-government extremists left a truck bomb outside a federal building in Oklahoma City in 1995. But in New York, no-one knew that yet.

At first it seemed like an accident. As long as skyscrapers and aeroplanes had co-existed, this was a nightmare waiting to come true. It was only 17 minutes before the world realised the nightmare was much, much worse.

At 9.03 am, United Airlines Flight 175 from Boston to Los Angeles, approached Manhattan, clearly too low, and smashed into the south face of the South Tower, between floors 77 and 85. It was broadcast live on television, and a global audience suddenly understood this was no accident. These were deliberate, coordinated, merciless attacks on America’s biggest city.

Three minutes before the impact, a passenger on Flight 175, Peter Hanson, used an Airfone to call his father in Connecticut. His final words remain chilling.

“I don’t think the pilot is flying the plane. I think we are going down. I think they intend to go to Chicago or someplace and fly into a building. Don’t worry, Dad. If it happens, it’ll be very fast… Oh, my God… oh, my God, oh, my God.”

They hit the South Tower at 587 mph. Carrying 34,000 litres of aviation fuel, the plane was a missile. All 65 people on board died instantly, incinerated. More than 600 remained above the 77th floor; 18 would escape down the one surviving stairwell, while the others probably died within minutes. Four jumped or fell to their deaths.

President George W. Bush was visiting an elementary school in Florida that morning. Before he entered a classroom, he was told of the terrible accident, a small aircraft hitting the World Trade Center. At 9.10 am, as he listened to second-graders read aloud, his chief of staff, Andrew Card, whispered in his ear.

“A second plane hit the second tower. America is under attack.”

That moment was immortalised by news cameras. Bush’s composure was extraordinary. He nodded slowly and began chewing his lip, and said nothing.

It was not over. At 9.37 am, an American Airlines Boeing 757 smashed into the west side of the Pentagon in Virginia. All 64 aboard were killed, the impact and subsequent structural damage causing 125 fatalities in the building itself. Donald Rumsfeld, the 69-year-old secretary of defense, went from his office to the impact site and helped tend to the injured – we should remember that.

The devastation was beyond anyone’s imagination. Three airliners had been turned into munitions, scaled-up versions of the Japanese kamikaze suicide pilots in the Second World War. The loss of life by now had to be over 1,000. Then things got worse.

At 9.59 am, the World Trade Center’s South Tower, the second to be struck, collapsed. It had stood 1,362 feet tall, one of the tallest buildings in the world, but the impact of an airliner at nearly 600 miles per hour, shearing through concrete and steel, was unsurvivable. It burned for 56 minutes, then the sagging floors pulled on weakened perimeter columns, and the uppermost stories dropped vertically onto those below all the way to the ground. It was unstoppable.

Another aircraft was still in the air. United Airlines Flight 93 had been hijacked at 9.28 am. The passengers knew what had happened to the other planes. At 9.55 am the Boeing 757 turned towards Washington. Tom Burnett, a 38-year-old businessman from California, agreed with other passengers that they had to get control of the aircraft back from the hijackers, or… everyone understood. Burnett ended his last call to his wife, “Don’t worry, we’re going to do something”.

Todd Beamer, another passenger, had explained the situation to an Airfone operator, Lisa Jefferson. At 9.57 am, she heard muffled voices and Beamer replying, “Are you ready? OK. Let’s roll.”

The voice recorder in the cockpit captured the sound of the food cart ramming into the cockpit door. At 10.03 am, the aircraft crashed in a field in Stonycreek, Pennsylvania, killing everyone on board. It was 20 minutes’ flying time from Washington, and the target had been the US Capitol.

At 10.28 am, the North Tower collapsed.

The eventual death toll of the 9/11 attacks was 2,977, from at least 102 countries. The injured may have numbered as many as 25,000. It took eight months to clear the debris from Ground Zero, while the final new building on the site, 2 World Trade Center, is due to be completed in 2031.

By 9.30 pm, George Tenet, director of central intelligence, was able to tell the President who was responsible: al-Qa’eda, the Islamist terrorist organisation which had blown up the US embassies in Nairobi and Dar-es-Salaam in 1998, killing 224, and carried out a suicide attack on the destroyer USS Cole in Aden in 2000.

The head of al-Qa’eda was Osama bin Laden, one of 52 children of construction magnate Muhammad bin Ladin, by his death in 1967 the wealthiest non-royal Saudi. In 1996 and 1998, bin Laden had issued fatwas condemning the United States’ military presence in Saudi Arabia, but even before that the CIA had had a dedicated unit monitoring his activities, so-called Alec Station.

19 hijackers had taken part, most Saudi Arabian, alongside two Emiratis, an Egyptian and a Lebanese. Only one was over 30, the youngest were 20. Three were known to the intelligence community, two having been under intermittent surveillance.

The world changed 25 years ago. It was shocked, and America’s sense of self altered forever. War had come to Manhattan. Yet no new factors enabled al-Qa’eda: no new technology, no new opportunity, no new resources. There had been commercial jet aircraft flights since 1952, the first skyscraper was completed in 1885, the first hijacking occurred in 1919.

All that was new was imagination. The planners of al-Qa’eda had the evil genius to weaponise the everyday and inflict an unhealable wound on their enemy. Some in US intelligence had toyed with the scenario, but dismissed it as unrealistic.

George W. Bush, only nine months into his presidency, set aside his platform of “compassionate conservatism” which focused on education, reducing poverty and leveraging international aid. Instead he declared a “Global War on Terror”, in which no-one was neutral.

“Either you are with us, or you are with the terrorists.”

On 14 September, the President stood atop the debris on Ground Zero and spoke through a bullhorn to the first responders on the site: “I can hear you. The rest of the world hears you. And the people who knocked these buildings down will hear all of us soon.”

The scope was as huge as the battle lines were stark: “it will not end until every terrorist group of global reach has been found, stopped and defeated”. By that measure, the war goes on.

Eliot Wilson is a writer and historian. He is a senior fellow for national security at the Coalition for Global Prosperity and a contributing editor at Defence on the Brink