LONDON Powerful military elites ultimately decided the outcome of Egypt and Tunisia's revolutions, but in Libya it is the much more opaque and complex tribal power structures that could decide how events play out.
Colonel Muammar Gaddafi has long relied on his immediate -- but small -- Qathathfa tribe to staff elite military units and guarantee his personal security and that of his government, experts say. But that is seen unlikely to be enough to secure the country.
More important are the larger tribes long co-opted into his rule such as the Wafalla, who make up an estimated 1 million of Libyan's more than 6 million population. Some rumours suggest the ferocity of Gaddafi's crackdown on his own people may already be prompting tribal leaders to switch allegiance.
"In Libya, it will be the tribal system that will hold the balance of power rather than the military," said Alia Brahimi, head of the North Africa program at the London School of Economics.
"I think you will see defections of some of the main tribes if that is not happening already. It looks like he has already lost control of the east of the country where he was never popular and never fully managed to consolidate his power."
Eastern Libya is the site of much of its oil reserves. On Tuesday, a Reuters correspondent reported that Gaddafi's forces appeared to have abandoned their positions on the border with Egypt which were now in the hands of men armed with clubs and Kalashnikovs who said they were opposed to his rule.
Who, if anyone, those men were answering to was not immediately clear. While herder and tribal lifestyles have declined in Libya in the face of rising oil-fueled urbanization, traditional power structures are said to remain strong beneath the surface.
In Egypt and Tunisia, the armies proved to be the supreme political force, easing unpopular leaders Hosni Mubarak and Ben Ali from office in part due to their reluctance to fire on protesters. Libya is very different, however.
Long largely closed to outsiders, details of its complex mix of alliances and loyalties are scarce. Experts generally agree part of Gaddafi's strategy for retaining power has been to keep his own tribe in important positions.
Key members of his family are said to command their own military formations, again usually members of their own Qathathfa tribe. Once largely nomadic herders, the Qathathfa were sidelined by Libya's former monarchy but allowed to join the armed forces and police, then considered secondary organizations.
Having risen through the military structure himself, Gaddafi is seen to have tried to emasculate it to prevent rival commanders from threatening him. Memorably, he abolished all ranks above his own position of colonel.
Gaddafi's unique "Green Book," containing his political philosophy and system of government, vows to put an end to tribalism but in reality experts say it entrenched it.
"Gaddafi has largely dismissed the older tribal military structures but they will probably not have huge problems finding weapons," said the LSE's Brahimi. "Defections from the military will be key to this."
Parts of the military had long appeared reluctant to use excessive force against their own people, she said. Popular rumor held that Gaddafi was forced to rely on Serbian mercenary pilots to bomb civilian areas during offensives against Islamist militancy in the 1990s.
DIVIDE AND RULE
Some say Gaddafi's tribal strategy has effectively amounted to a system of divide and rule, buying off particularly established tribal leaders from key groups. In recent years, they say, control has been faltering and recent events may accelerate this.
"Gaddafi made sure to keep the people aware of their tribal divisions, winning the alliance of larger ones and hence keeping the population under control," wrote Jerusalem-based journalist Lisa Goldman after a Skype conversation with a Libyan contact she said was well placed to talk on some military matters.
"Although the larger ones like the Werfalees and the Megrahees were privileged with power and money, his recent actions angered these tribes and for the first time in decades tribal barriers have withered away. People are uniting with other formerly rival tribes or even different ethnicities like the Amazeegh or Berbers."
If Gaddafi can persuade other tribes to stay loyal to him, most experts believe he will probably try to arm them directly, raising the risks of ethnic conflict that could tear the country apart, send refugees pouring into its neighbors and jeopardize oil supplies.
Gaddafi's opponents accuse him of bringing in mercenaries from elsewhere in Africa, perhaps veterans of civil wars in the Sahel and West Africa.
"There's a lot of weapons in the country and Gaddafi has armed tribes before that have supported him," said Geoff Porter, North Africa analyst and contributor to political risk consultancy Wikistrat.
"We could see something more along the lines of Lebanon's civil war -- a prolonged period of violence and bloodshed."
(Editing by Andrew Dobbie)