With remarkable resilience, unarmed protesters demanding reforms from Yemen's autocratic government have thronged the streets for the past seven months and braved a violent crackdown by government forces that killed hundreds.
But their uprising has been hijacked by Yemen's two traditional powers _ the tribes and the military _ all but ensuring that even if a new regime emerges from the chaos, it will not look or act much differently from the old one.
"Today, our revolution is at a crossroads," said protester Mansour Hamed. "It can either triumph through peaceful means or the whole nation will slide into civil war, in which case the military and the tribes will have stolen our revolution."
Breakaway military units and tribal fighters have been battling for more than a week in the capital with troops loyal to President Ali Abdullah Saleh, in fighting that has escalated since the president returned last week from Saudi Arabia, where he had been undergoing treatment for nearly four months for wounds suffered in an assassination attempt. As a result, turmoil has deepened in this divided nation, where the United States wants to preserve a focus on fighting al-Qaida militants.
The ruinous urban warfare has caught protesters in the middle _ and as a result they make up the bulk of more than 150 people killed in the fighting.
Moreover, it is threatening to turn the protest movement into a sideshow. The tribal chiefs and army commanders who switched sides and joined the opposition have already taken over an uprising that initially was engineered mostly by pro-reform youth groups with a vision for a democratic and free Yemen.
Inspired by popular uprisings in Tunisia and Egypt, Yemen's peaceful protests brought together a diverse mix of people in massive demonstrations _ sometimes drawing millions _ across this impoverished Arab nation. They shattered Yemen's entrenched gender, tribal and age barriers in a rare show of unity in a patriarchal and deeply religious society where tribal loyalties prevail and regional rivalries are common.
"The revolution has given birth to a whole new generation that has become aware of its potential," said Magid al-Madhaji, a protest leader and rights activist. "Their resistance to Yemen's traditional forces will continue."
The heavy hand of the military and tribes has already weakened the protest movement. The mostly liberal, left-leaning Yemenis of the south, for example, reduced their profile in an uprising they see as now led by Islamists and army commanders who have persecuted them for years.
"The traditional forces are delaying our victory," said Lina al-Hosny, an opposition activist from the southern port city of Aden. "If this continues, the revolution will fail."
Over the past week, Saleh's loyalists have shelled crowds of demonstrators, and bombardment exchanges have flown back and forth over Sanaa, the capital, between the elite Republican Guard troops led by Saleh's son Ahmed and the troops of renegade army general Ali Mohsen al-Ahmar.
During the fighting, al-Ahmar's forces sought to expand areas under their control in Sanaa by marching behind protesters advancing out of their seven-month-old encampment in Change Square, the epicenter of the uprising in central Sanaa.
Al-Ahmar's soldiers swiftly moved to take over those areas from the protesters and set up fortified positions, a tactic that, according to protest leaders, has drawn heavy retaliation from loyalists firing mortars and antiaircraft guns.
"They (renegade soldiers) gave forces loyal to Saleh an excuse to hit us hard and, at the end, we lost those new positions," said al-Madhaji, the protest leader. "We paid a very high price for the mistakes of the 1st Armored Division," he said, alluding to al-Ahmar's elite unit which boasts about 20,000 men in Sanaa alone.
Al-Ahmar, a veteran of Yemen's domestic wars over the past three decades, is widely thought to seek the presidency himself, which may have been behind his decision to switch sides in March and join the opposition.
But al-Ahmar is deeply distrusted by the protesters because of his years of close connection with the president. He is also tainted by human rights violations during a long-running war against Shiite rebels in the north.
"He is the other face of Saleh and the regime," said al-Hosny, the activist from Aden.
An impoverished nation of some 25 million people, Yemen is of strategic value to the United States and its Gulf Arab allies, particularly Saudi Arabia. It sits close to the major Gulf oilfields and overlooks key shipping lanes in the Red and Arabian seas. It is also home to what is perhaps the world's most active al-Qaida branch, whose militants already have taken advantage of the country's turmoil to capture and hold territory in the nearly lawless south.
Saleh, who has been in office for 33 years, has staunchly refused to quit power, balking at signing a deal that the United States and Saudi Arabia have backed in hopes of providing a smooth transition of power. Under the agreement, Saleh would resign and hand power to his vice president in return for immunity from prosecution.
Saleh spoke to the nation in a televised address Sunday. He again refused to step down, saying he would only do so after presidential elections. Yemenis are scheduled to chose a new president in 2013, but Saleh has floated the possibility of an earlier vote. He never said whether he would run in the next presidential elections.
That leaves the possibility of a dragged out fight among the traditional powers _ the military and the tribes _ that have long dominated the country and are now deeply divided.
Many in the protest movement believe regional powerhouse Saudi Arabia is playing a major role in shifting the uprising toward the tribal leaders and army commanders who have long been beneficiaries of its largesse.
Oil-rich Saudi Arabia has over the years invested heavily in Yemen, with which it has a porous border of some 1,000 kilometers (650 miles). It is known to run an elaborate and generous patronage system, paying Yemeni politicians, tribal leaders, top military officers and even Cabinet ministers.
An ultraconservative nation with little or no appetite for Western-style reform, Saudi Arabia will be unhappy to see the sort of democratic Yemen envisaged by the protesters, which would conceivably be more difficult for it to influence and offer an alternative to the kingdom's own political system, in which the monarch, King Abdullah, rules with absolute powers.
"Saudi Arabia does not want the revolution to succeed in Yemen and does not want to see Yemen in total chaos either," said analyst Abdul-Bary Taher of the state-owned Center for Yemeni Studies.
"It wants to see Yemen divided, humbled and unable to improve its conditions."
Hendawi reported from Cairo.