Cairo ? Cries of “Egypt is free” rang out and fireworks lit up the sky as hundreds of thousands danced, wept and prayed in joyful pandemonium after 18 days of peaceful pro-democracy protests forced President Hosni Mubarak to surrender power to the military, ending three decades of authoritarian rule.

Ecstatic protesters in Cairo’s Tahrir, or Liberation, Square hoisted soldiers onto their shoulders Friday and families posed for pictures in front of tanks in streets flooded with people streaming out to celebrate. Strangers hugged each other, some fell to kiss the ground, and others stood stunned in disbelief.

Chants of “Hold your heads high, you’re Egyptian” roared with each burst of fireworks overhead.

“I’m 21 years old and this is the first time in my life I feel free,” an ebullient Abdul-Rahman Ayyash, born eight years after Mubarak came to power, said as he hugged fellow protesters in Tahrir Square, where crowds remained all through the night.

An astonishing day in which hundreds of thousands marched on Mubarak’s palaces in Cairo and Alexandria and besieged state TV was capped by the military effectively carrying out a coup at the pleas of protesters. After Mubarak’s fall, the military, which pledged to shepherd reforms for greater democracy, told the nation it would announce the next steps soon. Those could include the dissolving of parliament and creation of a transitional government.

Ripple effects

Mubarak’s downfall at the hands of the biggest popular uprising in the modern history of the Arab world had stunning implications for the United States and the West, Israel, and the region, unsettling rulers across the Mideast.

The 82-year-old leader epitomized the complex trade-off the United States was locked into in the Middle East for decades: Support for autocratic leaders in return for stability, a bulwark against Islamic militants, a safeguard of economic interests with the oil-rich Gulf states and peace — or at least an effort at peace — with Israel.

The question for Washington now was whether that same arrangement will hold as the Arab world’s most populous state makes a potentially rocky transition to democracy, with no guarantee of the results.

The United States at times seemed overwhelmed during the upheaval, fumbling to juggle its advocacy of democracy and the right to protest, its loyalty to longtime ally Mubarak and its fears the fundamentalist Muslim Brotherhood — or more radical groups — could gain a foothold. Mubarak’s fall came 32 years to the day after the collapse of the shah’s government in Iran, the prime example of a revolution that turned to Islamic militancy.

In Egypt, persecuted democracy activists frequently denounced the U.S. government for not coming down harder on Mubarak’s rights abuses. Washington’s mixed messages during the crisis frustrated the young protesters. They argued that while the powerful Brotherhood will have to be allowed to play a future political role, its popularity would be diminished in an open system where other ideologies are freed to outweigh it.

Neighboring Israel watched with the crisis with unease, worried that their 1979 peace treaty could be in danger. It quickly demanded on Friday that post-Mubarak Egypt continue to adhere to it.

Any break seems unlikely in the near term. The military leadership supports the treaty. Anti-Israeli feeling is strong among Egyptians, and a more democratic government may take a tougher line toward Israel in the chronically broken-down peace process. But few call for outright abrogating a treaty that has kept peace after three wars in the past half-century.

More upheaval?

From the oil-rich Gulf states in the east to Morocco in the west, regimes both pro- and anti-U.S. could not help but worry they could see a similar upheaval. Several of the region’s rulers have made pre-emptive gestures of democratic reform to avert their own protest movements.

The lesson many took: If it could happen in only three weeks in Egypt, where Mubarak’s lock on power appeared unshakable, it could happen anywhere. Only a month earlier, Tunisia’s president was forced to step down in the face of protests.

“This is the greatest day of my life,” Nobel Peace laureate Mohammed ElBaradei, whose young supporters were among the organizers of the protest movement, told The Associated Press.

“The country has been liberated after decades of repression,” he said adding that he expects a “beautiful” transition of power.

Perhaps most surprising was the genesis of the force that overthrew Mubarak.

The protests were started by a small core of secular, liberal youth activists organizing on the Internet who only a few months earlier struggled to gather more than 100 demonstrators at a time. But their work through Facebook and other social network sites over the past few years built greater awareness and bitterness among Egyptians over issues like police abuse and corruption.

“Facebook brought down the regime,” said Sally Toma, one of the main protest organizers.

When the online activists called the first major protest, on Jan. 25, they tapped into a public inspired by Tunisia’s revolt and thousands turned out, beyond even the organizers’ expectations. From there, protests swelled, drawing hundreds of thousands.