Unlike in Egypt or Tunisia, it is not the conventional military that holds the balance of power in Libya.
Instead, it is a murky network of paramilitary brigades, “revolutionary committees” of trusted followers, tribal leaders and imported foreign mercenaries.
The actual Libyan Army is almost symbolic, a weakened and emaciated force of little more than 40,000, poorly armed and poorly trained. It is part of Col Muammar Gaddafi’s long-term strategy to eliminate the risk of a military coup, which is how he himself came to power in 1969.
So the defection this month of some elements of the army to the protesters in Benghazi is unlikely to trouble Col Gaddafi. Not only can he do without them, his security apparatus has not hesitated to call in air strikes on their barracks in the rebellious east of the country.
So, who is propping up his regime and allowing it to stay in power while two of its neighbouring leaders have fled amid a massive momentum for regime change throughout the Middle East?
Internal Security
Like many countries in the region, Libya has an extensive, well-resourced and brutal internal security apparatus.
Think East Germany’s Stasi or Romania’s Securitate pre-1989, where no-one dared criticise the regime in public in case they were reported to the feared secret police, and you can see the similarities.
During my own visits to Libya I have always found it hard to get ordinary people to speak freely on the record to a journalist, as government “minders” are always watching and noting who says what.
Some of Col Gaddafi’s own sons have worked in internal security but today, the key figure in Libya’s security apparatus, both internal and external, is Gaddafi’s brother-in-law, Abdullah Senussi.
A hardliner with a thuggish reputation, he is strongly suspected of being the driving force behind the violent suppression of protests, notably in Benghazi and the east of the country.
As long as he keeps advising Gaddafi to tough it out there is little chance of his stepping down.
The Paramilitaries
Libya has a number of “special brigades” answerable not to the army but to Gaddafi’s Revolutionary Committees.
One of these is believed to be commanded, at least nominally, by one of Col Gaddafi’s maverick sons, Hannibal, who clashed recently with Swiss police in Geneva after allegations he abused hotel maids there.
The paramilitaries, sometimes known as the “People’s Militia”, have so far been largely loyal to Col Gaddafi and his close circle known in Arabic as Ahl al-Khaimah - “People of the Tent”.
If the paramilitaries changed sides and joined the protesters en masse this would seriously undermine Col Gaddafi’s ability to survive.
The Mercenaries
This has been one of the darker and particularly disturbing facets of the Libyan uprising.
There are persistent reports that Col Gaddafi’s regime has been making extensive use of hired African mercenaries, mostly from the Sahel countries of Chad and Niger, to carry out atrocities against unarmed civilian protesters.
Libyan witnesses say they have been firing from rooftops into crowds of demonstrators, in essence carrying out the orders that many Libyan soldiers have refused to obey.
Col Gaddafi has long fostered close relations with African countries, having turned his back on the Arab world some time ago, and there are an estimated 500,000 African expatriates in Libya out of a total population of six million.
The number of those serving as pro-Gaddafi mercenaries is thought to be quite small but their loyalty to his regime is said to be unquestioned and there are reports of extra flights being laid on to bring in more in recent days.
The Tribes
Libya, like the other Arab revolutionary republics of Yemen and Iraq, is a country where your tribe can help define your loyalties, but in recent years the tribal distinctions have blurred and the country is less tribal now than it was in 1969.
Col Gaddafi himself comes from the Qadhaththa tribe. During his 41 years in power he has appointed many of its members to key positions in his regime, including those for his personal safety.
Just as Saddam Hussein did in Iraq and President Saleh has in Yemen, Col Gaddafi has been adept at playing off one tribe against another, ensuring that no one leader risks posing a threat to his regime.
Libya-watchers are now speculating whether Col Gaddafi’s regime will carry out its own self-fulfilling prophecy of civil war and deliberately arm the tribes loyal to the regime to put down the protest that has already seen it lose the eastern half of the country.
by Frank Gardner