The US-led effort in Iraq has reached its most critical point since the invasion began just over a year ago.
The fierce fighting this week between major religious factions and American soldiers could be more critical to the eventual outcome than even the largely-symbolic fall of Baghdad and the capture of Saddam Hussein.
Defense Secretary Donald Rumsfeld calls it "a test of will." But it's also a test of US military preparedness and capability, coalition unity, reconstruction and nation-building efforts, and the Bush administration's exit strategy (starting with the planned handover of sovereignty to an Iraqi government 10 weeks from now).
Other factors are even more unclear. The strength and motives of opposing factions in Iraq, and the involvement of other countries - principally Iran - in resisting the US administration, are difficult to gauge, as is US public opinion as the nation moves towards its first wartime presidential election in a generation.
What are the Bush administration's options?
According to a range of experts, it largely hinges on whether one believes the invasion was a good idea in the first place.
The rebellion instigated by radical Shiite cleric Moqtada al-Sadr "is less a political movement than ... [a manifestation of] the flocking of disenfranchised young men to charismatic leaders who promise them some power and a place in society," says Loren Thompson of the Lexington Institute in Arlington, Va. "It's not a new story, and not a hard impulse for well-trained US troops to contain," says Mr. Thompson.
But trying to contain well-armed Shiites (as well as Sunni Muslims) willing to fight the greatest military force on earth puts the Bush administration in a bind.
"If US forces respond too weakly, they will embolden both sets of insurgents," says military analyst Ivan Eland of the Independent Institute in Oakland, Calif. "If they respond muscularly - [which is] the US military's, particularly the Army's, natural response and the goal of the insurgents - they risk inflaming the entire population."
The US bomb and rocket attack Wednesday on a mosque used by armed insurgents may be legal under the Geneva Convention rules of war. But it makes for poor public relations, even among Iraqi civilians happy to have been liberated from the Hussein regime.
Dr. Eland's suggestion is to partition the country along ethnic and factional lines -- Shiite, Sunni, and Kurdish - and withdraw in an orderly but deliberate fashion.
That seems unlikely for a variety of reasons, particularly given the administration's ultimate goal of creating a democratic, unified Iraq.
But the fierce urban combat involving two of those factions could make that goal elusive. The recent backlash of the Shiite faction led by Sadr, some experts worry, could have broader consequences for the whole region.
"The problem at this moment is that it is unclear whether this is the last gasp of a small guerrilla group, or the opening move in a proxy war with Iran," says John Pike, director of GlobalSecurity.org. Sadr reportedly is being supported by Iran (a largely Shiite country) and the terrorist group Hizbollah, which was started in Iran and now is based in Lebanon.
"In the short term, the only option is to engage the enemy when and where he can be found," says Mr. Pike. "In the midterm, the process of Iraqification needs to continue and the US needs to do more to support the development of civil society."
"The reconstruction contracting mess needs to be straightened out" as well, says Pike. While some analysts and members of Congress raise the specter of a Vietnam-like "quagmire," others say failure would more likely resemble Israel's 37-year experience occupying Palestinian territory. Indeed, some insurgents have been describing the events of the past week as an "intifada."
"If the current situation unravels, the US military will be faced with its own version of the Israeli occupation of the West Bank, where military action to suppress the insurgency creates more new insurgents and an endless cycle of violence," warns defense analyst Charles Penã of the Cato Institute in Washington.
US officials insist that they will not allow this to happen.
"As President Bush has said, we did not charge hundreds of miles into the heart of Iraq and pay a bitter cost of casualties [635 US military deaths and 2,988 wounded so far] to liberate 25 million people, only to retreat before a band of thugs and assassins," Secretary Rumsfeld said this week. "We're facing a test of will, and we will meet that test."
Many members of Congress - Democrats and Republicans alike - have urged the administration to increase the number of US troops in Iraq, which would reverse current plans to reduce US force levels.
Confirming that this is a possibility - at least in the short term - the chairman of the Joint Chiefs of StaffGen. Richard Myers says some troops scheduled to be rotated back to the US may be ordered to stay beyond one year, even as fresh troops move in to replace them.
That ultimately will be decided by Army Gen. John P. Abizaid, commander of US military operations in the Persian Gulf region.
Others note the need to strengthen and bolster what looks like an increasingly tenuous US-led coalition, many nations of which have proven to be inneffective militarily. Ukrainian forces, for example, withdrew from the area they were meant to secure and a Bulgarian unit called for US backup.
"The coalition is beginning to weaken," says retired Air Force Col. Sam Gardiner. "Singapore troops returned home this week. Norway has said it is going to focus on peacekeeping in other parts of the world.
South Korea is sending a team this week to reassess the situation. Portugal seems to be weakening.
"Like Vietnam, it's not that it was not possible to be successful, but the question is whether or not we are willing to pay the price," says Colonel Gardiner. "The price for Iraq has just gone up."