The shock was most acute in the United States, but the impact rumbled across the globe in a massive military mobilization, in the hasty assembling of a diplomatic coalition against terrorism, in the accelerated decline of the world economy that had looked so healthy as 2001 began.
Swarms of people fled Afghanistan toward Pakistan or Iran, fearing the inevitable fury of U.S. military strikes against the nation that accepted Osama bin Laden as its guest.
In the wider world some companies collapsed, jobs disappeared, airlines went out of business.
Wherever you lived, life became scarier.
"We are staring into the face of the first synchronized world recession of the globalization era," said Juan Somavia, director general of the International Labor Organization. The U.N. agency estimated that the impact of the attacks would put 24 million people out of work, and sink 15 million more into deeper poverty.
The suicide attacks posed a monumental challenge to President George W. Bush, so recently disparaged in many foreign publications as the dimwitted winner of a suspect election.
Traditional U.S. allies had been stung by Bush's unilateral decision to dump the Kyoto accord on global warming, or were alarmed by his plans for a missile defense system. Now they vied for a shoulder-to-shoulder position with the American leader.
Their reaction was instinctive, seeing the devastation in New York as an attack on democracy and capitalism. But analysts suggested some leaders jumped into the coalition partly in hopes of restraining any impetuous retaliation by an untested president.
"The attack against the United States shows with devastating and tragic clarity that no single country can withdraw from the world. Isolationism and missile shields don't offer any protection against domestic planes that have been hijacked," Stockholm's Expressen newspaper editorialized the day after the attack.
Bush held his fire, built his alliance and rose in stature.
Just the previous month, polls conducted by the Pew Research Center for the People and the Press had found that half or more of the respondents in France, Germany, Britain and Italy disapproved of Bush's handling of foreign policy.
Now all four governments offered troops and other support for the military campaign in Afghanistan, with a British submarine joining the first day of the attacks. Since Sept. 11, opinion polls in Britain have pegged Bush's approval rating around 70 percent.
Hardly any government beyond Baghdad dared to endorse the attacks on the World Trade Center and the Pentagon, but many saw opportunities to recast their own problems as part of the Americans' international crusade.
Israeli Prime Minister Ariel Sharon repeatedly compared Palestinian leader Yasser Arafat to Osama bin Laden. Syrian President Bashar Assad condemned "stae terrorism," and meant Israel.
Russian President Vladimir Putin drew a parallel with his country's war in Chechnya, and found the West suddenly more sympathetic.
Robert Mugabe's government in Zimbabwe claimed to have detected terrorists operating in the political opposition and even in some news organizations.
China detected the local branch of international terrorism in the form of Turkic-speaking Uighur rebels in Xinjiang province. "The fight against separatists in Xinjiang is part of the fight by the world against terrorism," Foreign Ministry spokesman Zhu Bangzao told reporters.
The attacks had a swift and chilling impact on economic activity. For several days the New York Stock Exchange was closed, all U.S. flights were grounded and international airlines canceled flights to the United States.
Economic forecasts were hastily revised. The World Bank said world trade was likely to grow by less than 2 percent in 2001, compared with 13 percent the previous year.
"Weakening global growth, falling commodity prices, increased refugee flows, and loss of tourism earnings will adversely affect most of the world's poorest countries, and keep millions of people from climbing out of poverty," World Bank President James D. Wolfensohn said in November.
"In economies that stall or fall into recession, the number of people living on less than $1 per day will actually increase."
All that had passed in the first nine months of 2001 paled into insignificance on Sept. 11, tumultuous though those events had been.
Yugoslavia's Slobodan Milosevic was brought before a U.N. war crimes tribunal. An American named Dennis Tito became the first tourist in space. Animal diseases decimated European farming. A world conference to promote racial tolerance dissolved into acrimony. China and the United States squared off over a spy plane. AIDS and war continued to devastate Africa.
And the world moved on: China joined the World Trade Organization the last communist giant now bound firmly into the global trading system. Europe forged ahead with its single currency, the euro, a symbol of a continent's resolve never to descend into war again.
But if priorities were changed on Sept. 11, all the familiar problems endured.
"The rest of the world did not go away because New York was attacked," said Jody Williams, a Nobel Peace Prize winner in 1997 for the International Campaign to Ban Landmines.
"There are many many problems in the world we need to address, not just that one."
By Robert Barr
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