LONDON Libyan rebel forces ill-equipped to fight their way into a city the size of Tripoli may look to locally brokered deals or a burgeoning popular uprising to break the will of Muammar Gaddafi's forces.
Libya's civil war so far has involved some serious urban fighting in towns such as Misrata, but most battles have been relatively small skirmishes.
If Libyan leader Muammar Gaddafi retains the loyalty of large numbers of security forces in the capital, the ragtag opposition forces could struggle and there would be little NATO air strikes could do without risking civilians.
"I'm assuming the Tripoli fighting could be the fiercest," said Hayat Alvi, lecturer in Middle East politics at the United States Naval War College. "The wild card will be the Tripoli public. True loyalties will have to finally manifest themselves. I'm predicting in the rebels' favor, but we don't know what Gaddafi and his sons have up their sleeves."
Gauging the loyalty of Tripoli's population is far from easy. Gaddafi loyalists have put on many marches and demonstrations of loyalty in recent months, but hundreds if not thousands of his opponents also took to the streets in the early stages of the uprising before they were cowed.
The rebels will hope security forces will melt away.
Some say Gaddafi himself might already have fled, perhaps to his hometown of Sirte or a desert base further south. The long speeches at boisterous public meetings have given way to broadcast addresses delivered on scratchy telephone lines.
But others say the nascent uprising reported in Tripoli on Saturday night might have come too soon, with opposition forces still too far away to help. Despite rhetoric of taking Tripoli and ending the war in hours or days, some analysts suspect it is more likely the rebels will cement their stranglehold on the city and then see how events play out.
"I think they'll wait on the outskirts and hope for either an uprising or that Gaddafi decided to call it a day and leaves," said David Hartwell, Middle East analyst for IHS Jane's. "If they do go in, they could find it very difficult and they will be keen to avoid that. It's relatively obvious that NATO has been providing close air support for the rebels.
"That's one thing in open countryside or lightly populated areas -- although it pushes the Security Council mandate, to put it mildly -- but it would be almost impossible in Tripoli."
KEY FIGURES ALREADY GONE?
Gaddafi's government seems keen to broker some kind of last-minute ceasefire that would keep them in power. But few believe either the rebels or NATO would agree to that at this stage.
In Paris, a diplomatic source said rebel cells undercover in Tripoli were putting into action plans prepared months ago. He said, however, the rebels were under orders not to enact revenge killings or summary executions against senior members of Gaddafi's camp.
Saad Djebbar, a former lawyer for the Libyan government, told Reuters he believed many key figures loyal to Gaddafi had already fled to other countries in Africa such as Niger, Mali and Chad where they had good contacts.
"The big sharks have already left the scene, he said. "It's not going to be Stalingrad. Tripoli is very small. People know each other. People negotiate their way forward. Gaddafi is bound to have some people who will put up a symbolic fight. But these are mostly thugs and there is no organized force left of any size to check the rebels."
If the rebels are wrong and significant Gaddafi forces remain, strategists say they could be in serious trouble. Urban warfare is notoriously challenging and bloody, giving a clear advantage to the defender, while some doubt the opposition have sufficient supply lines to sustain an offensive.
"The costliness of urban fighting cannot be overestimated," said political risk consultancy Stratfor in a note. "Such warfare requires a well-trained force with high morale, and the rebel forces in the west are known to be few in number... and extremely ill-trained."
The key battle now, Stratfor said, was psychological -- with the rebel agenda to paint a picture of inevitable victory that would enthuse new uprisings and prompt Gaddafi loyalists to abandon their cause to save their necks.
GADDAFI CHOICES KEY
Much, of course, will depend on how Gaddafi himself chooses to play the endgame. He could still perhaps go into either internal or external exile or simply try to copy Iraqi leader Saddam Hussein and disappear into the post-war chaos.
Saddam evaded U.S. forces for months following the 2003 fall of Baghdad before they eventually tracked him down -- although most analysts believe such a scheme would prove tougher in Libya because of its more disparate geography.
Even if opposition forces were able to take much of Tripoli relatively easily and bloodlessly, they might still struggle to take down the final remnants of the regime.
Then, the situation could resemble that seen earlier this year in Ivory Coast, where opposition fighters loyal to Alassane Ouattara took much of the capital Abidjan but seemed unable to capture incumbent leader Laurent Gbagbo.
It took the actions of French helicopter gunships and troops already based in the country to eventually breach his compound and bunker, allowing his capture by local forces.
The International Criminal Court in The Hague indicted Gadaffi, his eldest son and spy chief for crimes committed during their initial crackdown. That might yet prompt foreign military action to help the rebels capture him.
"I would have thought NATO would be very keen let the rebels get Gaddafi themselves as they possibly can," said IHS Jane's Hartwell. "But if it really came down to getting him out of a hole, you could see some Western involvement as we did in Abidjan. The ICC warrant could make it justifiable in that context." (Additional reporting by William Maclean and Catherine Bremer; editing by Ralph Boulton)
(Reporting By Peter Apps)