Libya: Who is propping up Gaddafi?

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.
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Internal Security

Like many countries in the region, Libya has an extensive, well-resourced and brutal internal security apparatus.
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The Paramilitaries

Libya has a number of "special brigades" answerable not to the army but to Gaddafi's Revolutionary Committees.
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The Mercenaries
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The Tribes
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http://www.bbc.co.uk/news/world-africa-12558066