March 8 (Reuters) - Libya's military before the insurrection was on paper made up of some 100,000 troops, backed by heavy artillery, tanks, warplanes and a small navy.
Since the rebellion there have been defections by members of the armed forces and some military hardware has fallen into rebel hands.
The level of rebel strength is difficult to ascertain, but the best equipped and trained units have remained loyal to leader Muammar Gaddafi because they are outside the regular army structure and are commanded by family members or people in his inner circle.
Here are some details of Libya's armed forces, officially totalling about 76,000 active personnel, plus a reserve or people's militia of some 40,000.
GROUND FORCES - STRENGTH ON PAPER:
Numbers: 50,000 including 25,000 conscripts.
Main Battle Tanks - 800, although many are thought to be inoperable.
Reconnaissance vehicles - 120.
Armoured Infantry Fighting vehicles - 1,000.
Armoured personnel carriers - 945.
Artillery pieces 2,421 (including 444 self-propelled, 647 towed).
Mortars - 500.
Air Defence surface-to-air missiles - at least 424.
GROUND FORCES - REALITY:
Even before the uprising, Libya's military strength was seen as having been seriously undermined by sanctions and neglect although Western powers had just began to sell it weapons again. Much of the equipment is seen as poorly maintained or unusable, leaving it hard to estimate genuine numbers.
Analysts say Gaddafi tried to emasculate the regular army to avoid the emergence of commanders who might rival his immediate family, relying instead particularly on three loyal "regime protection" units often of his own tribe.
That leaves him with what most estimate to be some 10-12,000 loyal Libyan troops. The most reliable formation is seen to be the 32nd Brigade commanded by Gaddafi's son Khamis.
Repeated reports from witnesses, rights groups and others talk of African mercenaries flown in by Gaddafi to help put down the revolt. Exact numbers are impossible to obtain.
In Libya's east around the city of Benghazi, regular military forces appear to have either defected to the opposition or melted away. Citizen groups also have taken up arms.
But analysts say the opposition lacks much in the way of command and control or even any form of centralised leadership.
NAVY - STRENGTH ON PAPER
Numbers: 8,000 including coast guard.
Submarines - 2 patrol submarines.
Surface vessels - 3
Patrol and coastal ships - 16
NAVY - REALITY
Libya's two surviving Foxtrot class diesel submarines were delivered by the Soviet Union in the late 1980s, but outside experts have long questioned their reliability. According to IHS Jane's, in 2003 one was reported to be in dry dock and one was sea going -- although unlikely to be fully operational. It suggested both might already have been abandoned.
AIR FORCE - STRENGTH ON PAPER
Combat capable aircraft - 394 (many non-operational, in store)
Seven bombers -- Tu-22
187 fighters -- 75 MiG-23, 15 MiG-23U, 94 MiG-25, 3 MiG-25U
180 fighter-ground attack -- 45 MiG-21, 40 MiG-23BN, 4 Mirage 5DP30, 14 Mirage F-1A, 3 Mirage F-1B, 15 Mirage F-1E, 53 Su-17M-2, 6 Su-24MK
Seven intelligence/surveillance -- 7 MiG-25R
35 Attack -- 23 Mi-25, 12 Mi-35
11 Maritime reconnaissance
55 Transport -- 4 CH-47C, 5 Bell 206, 46 PZL Mi-2
AIR FORCE - REALITY
Analysts estimate many of Libya's fast jets are in fact no longer airworthy. Gaddafi has so far also lost at least four aircraft in the course of this uprising with two jets defecting to Malta, one being shot down and the crew of a third ejecting over the desert rather than bomb opposition targets as ordered. There have been reports that rebels brought down a helicopter.
There are also Air Defence Command forces which possess at least 216 surface-to-air missiles and 144 towed and 72 self propelled missiles.
Again, maintenance may be an issue. Most analysts believe Libya's armed forces would not be able to seriously threaten outside air forces attempting to enforce a no-fly zone, saying Gaddafi's defence capabilities probably lag behind those of Iraq's Saddam Hussein before the US-led 2003 invasion.
The BBC reported a British RAF Hercules transport aircraft evacuating foreign nationals came under small arms fire but was not seriously damaged. Some suggested the attack might have come from opposition forces who mistook the plane for one of Gaddafi's aircraft on a bombing raid.
According to the Organisation for the Prohibition of Chemical Weapons (OPCW), Libya destroyed its entire stockpile of chemical weapons munitions in early 2004 as part of a rapprochement with the West that also saw it abandon a nuclear program.
The OPCW told Reuters Libya did retain some 9.5 tonnes of deadly mustard gas at a secret desert location but no longer had the capability to deliver it.
Sources: Reuters/IISS Military Balance 2011
(Additional reporting by David Cutler)