Within hours of U.S. missiles hitting Iraq, demonstrators and government leaders in many nations denounced the war as ill-advised, ill-conceived and ill-fated.
Hundreds of thousands of protesters thronged streets and squares, staged job walkouts and shouted their anger in a chorus meant to warn the Bush administration of increasing international outrage.
"We are disgusted," said Teresa Mohammed, who joined a rally that briefly stopped traffic in central London. "Everyone is in agreement about Saddam Hussein, but why do the Iraqi people have to suffer?"
In Germany, students ditched class to gather and yell slogans popular during protests against the Vietnam War. Italian activists blocked highways and sat on train tracks. Marchers in Paris chanted, "Bush, Blair, assassins!" Spanish cities such as Seville flew the flag at half-staff, in defiance of their government's support of the United States.
And in capital after capital, the war's onset inspired world leaders to go on national television, sometimes speaking in favor of the attack but more often criticizing it.
"The wrong decision was taken," German Chancellor Gerhard Schroeder said. "The logic of war has won out against the chances for peace. Thousands of people will suffer terribly."
Abdullah Ahmad Badawi, the deputy prime minister of Malaysia, called the attack "a black mark in history."
"A large and powerful nation ... has launched an attack against a sovereign state that has a diminished capacity to defend itself," he said.
Many of Thursday's mass protests were directed at U.S. diplomatic missions, causing local authorities to increase security around American embassies and consulates. In Greece, more than 100,000 demonstrators marched on the U.S. Embassy in Athens to accuse Americans of being killers.
It took 19-year-old Antje Krueger an hour by train to get from her hometown of Falkensee, Germany, to Berlin, where thousands of students converged on the historic Brandenburg Gate. "I had exams today, but I thought it was more important to come out for this," Krueger said. "What good does a diploma do me if there's a war on when I graduate?"
Several arrests were reported in London, but most of the day's protests were nonviolent. Passions often ran highest in countries whose governments have backed military action in Iraq over the broad opposition of their constituents.
Besides the U.S. and Britain, only Australia has sent troops to Iraq -- a move assailed by protesters who filled the streets of Australia's two biggest cities. More than 10,000 people marched through Sydney to declare "No blood for oil" and "Shame" to their prime minister, John Howard, while 20,000 rallied in Melbourne.
The debate over Iraq has exposed and exacerbated tensions between the United States and some of its allies and among those allies themselves, especially the countries of the European Union.
Leaders of the 15 EU nations met in Brussels on Thursday evening for a previously scheduled two-day summit that quickly became all about the start of the war. An attempt at a unified statement on helping the Iraqi people was overshadowed by reports of a rancorous confrontation at the table between British Prime Minister Tony Blair and French President Jacques Chirac.
"Let's say there were a great many interruptions in a very short time," said Belgian Prime Minister Guy Verhofstadt.
In a news conference before he left for the summit, the prime minister of Spain, Jose Maria Aznar, one of President Bush's closest allies, defended the use of force to battle a regime he accused of trampling human rights and harboring prohibited weapons.
"In this crisis, there is room neither for neutrality nor for indifference," he said. "There existed more comfortable options, but we do not want to postpone into the future the risks we must face in the present."
But in France, Chirac warned: "Whatever the duration of the conflict, it will bring weighty consequences for the future. Tomorrow, we will have to come together with our allies, with the whole international community, to meet together the challenges that await us."
Times staff writers David Holley in Moscow, Richard C. Paddock in Canberra, Australia, Sebastian Rotella in Paris, Janet Stobart in London and special correspondent Cristina Yanguas in Madrid contributed to this report.