"Tahrir," the man on the flatbed truck screamed hoarsely through a megaphone. "Freedom."
"Allahu Akhbar," cried the crowd of demonstrators in response. "God is great."
These marchers in the Jordanian capital were venting their anger at the U.S.-led war against the Iraqi government. And, across the Middle East, protesters like them are blending old pan-Arab nationalist sentiment with newer strains of Islamism. It is a wave of political ferment that some analysts say could spell more trouble for America and its allies in the region when the fighting in Iraq stops.
Already, governments friendly to Washington are distancing themselves from U.S. policy, heading off criticism in the street by chiming in with popular opinion. In doing so, they are lending credibility to opposition groups they normally prefer to ignore or repress.
As television images of dead and wounded Iraqi children beam across the Muslim world, "my worry is about the Arab street, that people watching these pictures are moved and could be mobilized," says Mai Yamani, a Middle East specialist at the Royal Institute for International Affairs in London. "They are part of a new movement of Arab nationalism that is radical ... that could erode the legitimacy of leaders in the region," she adds.
Other observers are more sanguine about the prospects for regional stability.
"If anyone is saying these huge demonstrations are regime-threatening, they are totally wrong," argues Abdel-Monem Said, head of the Al-Ahram Centre for Political and Strategic Studies in Cairo.
"Some of the opposition groups take advantage of the situation to criticize the government because they think it should do more," he says. "But soon enough everyone realizes that the government has the same position as they do."
Nowhere is this clearer than in pro-Western Jordan, which has allowed Washington to station several thousand troops on its territory during the war. Officially they are here to man Patriot anti-missile batteries, but Special Operations Forces are believed to have staged raids into the western Iraqi desert across the Jordanian border.
King Abdullah, however, has stepped up the level of his anti-war rhetoric in recent days, in the face of countrywide demonstrations.
Last week he condemned the U.S.-led "invasion" and expressed anger at "the growing number of martyrs among innocent Iraqi civilians."
"The government is actively engaged in a process to co-opt the opposition by allowing people to express their feelings," says Mustapha Hamarneh, a political analyst at Jordan University. "They are saying the king and the people are one in their opposition to the war."
Similar moves are evident further afield, such as Indonesia, where Vice President Hamzah Haz described President Bush as "the king of terrorists" in remarks after Friday prayers in Jakarta.
In Syria the government has organized anti-war marches and "chosen to align itself with the brotherly Iraqi people," in the words of an official spokesman.
In Turkey, the government went so far as to nix U.S. plans for a northern front in the war when parliament reflected popular opposition by refusing to allow coalition troops to move through the country.
And in Egypt, where protesters early in the war burned a poster of President Hosni Mubarak, the ruling National Democratic Party has since staged its own anti-war demonstrations and even used members of the banned Muslim Brotherhood to keep order.
Such tactics appear to have calmed the situation. In most countries of the Middle East, protests are now less frequent than at the beginning of the war.
Demonstrations in Jakarta against the war in Iraq have been smaller than protests against the U.S. assault on Afghanistan, and tensions on the streets of Amman have not reached the levels seen during massive marches last year against Israeli incursions into Palestinian-controlled areas of the West Bank.
But the war has demanded a careful balancing act from Middle Eastern governments friendly to the United States. "They are walking a tightrope between their public opinion and the West," says one Western diplomat in Amman.
On one hand, these governments are heavily dependent on the United States and Europe for military and economic aid, and even the richest Gulf states rely on U.S. demand for oil to keep prices high, as much as the U.S. relies on their oil.
On the other, their peoples are overwhelmingly sympathetic to Iraq in the current conflict, and even in some cases to Saddam Hussein, who is seen more as a symbol of resistance to an outside aggressor than a vicious despot.
After a string of military defeats over the past 35 years, Arabs from Morocco to Bahrain are drawing a sense of pride from Iraqi forces' continued opposition to the U.S. military juggernaut, although few expect that opposition to prevail.
"Everyone in the area is saying the same thing - that this campaign is against the Arab nation," explains Abdulateef Arabiyat, a leading Jordanian Islamist. "He who has been sleeping has woken up. The Americans are insulting everybody, not just Saddam Hussein or the Iraqis."
This attitude finds a firm foundation in the general sense of malaise that assails ordinary Arabs across the region - deprived of job prospects, political freedoms, and hope for the future.
In many cases, Arab governments proclaiming a pan-Arab nationalist ideology are held to blame for this state of affairs, and political parties driven by Islam find more support. But the current crisis has brought secular nationalists and religious leaders together under the umbrella of their common Arab identity.
In Jordan, for example, communists, Islamists and a former police chief joined in addressing a letter to the king last week demanding that he declare the war illegal.
"In the past the slogans were revolutionary. Now our kids demonstrate carrying Qurans, but basically it is the same sentiment of oneness" being expressed, says Hamarneh.
"Pan-Arab causes always unite people," he adds. "But they are united for the immediacy of the act - condemning the war. Nothing else unites them. Nothing political will come out of it."
This is partly because governments throughout the region have been careful, in more or less subtle ways, to prevent the emergence of credible and organized opposition movements. In some countries, such as Syria or the Gulf states, anti-government activity is simply illegal. In others, such as Jordan and Egypt, it is hedged about with electoral laws and press freedom decrees designed to limit its impact.
Forced underground into the dark and fevered world of secret cells, however, Arab hostility to America and its allies could bolster America's enemies in the "war on terror," observers in the region warn. "We know regimes won't allow people to organize massive demonstrations, so the trend now is to form small splinter groups to commit violence against Americans," says Hamarneh.
"Anti-Americanism is deepening," adds Said in Cairo. "There is a deep frustration with the U.S., and fundamentalists are capitalizing on it. Osama bin Laden is very happy with this war."