As government and rebel fighters battle for control of Ajdabiya, defence analyst Anthony Tucker-Jones looks at the strength of Gaddafi forces heading for Benghazi.

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Gaddafi troops celebrate on the outskirts of Ajdabiya (Reuters)

Saif al-Islam, Gaddafi's second son claims loyalist forces now control 90 per cent of the country and are poised to retake Benghazi within the next few days.

Some 2,000 Gaddafi loyalists supported by 50 tanks were employed to retake Zawiyah, west of Tripoli, with 200 commandos battling to secure the town centre after a 13-hour bombardment. Then to the east 4,000 men supported by dozens of tanks and commandos retook Ras Lanuf, while 1,500 troops and four tanks drove on to launch the attack on Ajdabiya.

Leading Gaddafi's counterattack are the Hamza, Hosban and Khamis Brigades. His power base draws on three tribes: the Maghraha, Qadhadfa (Gaddafi's tribe) and the Warfalla, whose men fill the ranks of these formations.

The key unit is the 10,000-strong elite 32nd Brigade, led by another of his sons, Khamis Gaddafi, who was trained at the Frunze Military Academy in Moscow. It was this unit that secured Tripoli in the opening stages of the rising and is now leading Gaddafi's attempts to reassert control of Libya. The brigade has been rather extravagantly described as the Praetorian Guard of the Gaddafi family, but such comparisons are ill-advised.

Firepower

Nonetheless, what the brigade lacks in military proficiency it easily makes up for in firepower, as well as tanks and artillery, it deploys the BM-21 122mm rocket launcher, which can deliver 40 rockets at once onto a target. They take just eight minutes to load and 20 seconds to fire. Loyalist PoWs have said these constitute their main striking power and have terrified opposition forces into flight. Its highly unlikely he has been able to muster the 10 tank and eight mechanised battalions listed in the Libyan Army's ORBAT, but this matters little.

At one point Gaddafi could call on 19 para/commando battalions, plus a Republican Guard force that is also considered a Special Forces unit. In addition, the Libyan Navy has a naval commando unit and a naval infantry battalion that can be transported in one of five landing ships. It is likely elements from these forces spearheaded the Ras Lanuf assault. The naval commando unit was equipped with six mini-submarines of the Yugoslav made R-2 Mala Class and some fast craft.

At least one Special Forces unit - known as the "Thunderbolt" squad has defected to the opposition. The latter's National Libyan Council claims it is supported by 8,000 regular troops, including 3,000 Special Forces which are ready to die defending Benghazi.

Gaddafi can also call on the People's Security Organisation and the Revolutionary Guard Corps, numbering around 3,000 strong. These are paramilitary units and are only equipped with small arms.

It's clear that Colonel Gaddafi has been relying on the Khamis Brigade, divided up into penny packs to bolster his other loyalist/mercenary forces. The bulk of his available tanks seem to have been used initially against Zawiyah after reports that up to a battalion of tanks had surrounded the town before overrunning it.

There have been signs of cracks in the 32nd Brigade's ranks, with reports of members of the unit defecting during attacks on Misrata.

In contrast tank forces attacking the opposition in the east have been limited in number. The audacious amphibious commando attack that helped retake Ras Lanuf was initially supported by just three tanks.

There have been signs of cracks in the 32nd Brigade's ranks, with reports of members of the unit defecting during attacks on Misrata. A Libyan Army spokesman has denied this.

Additionally Khamis Gaddafi was reportedly injured when a Libyan Free Air Force pilot crashed into the family stronghold at Bab Al Azizya on 15 March.

Following the recapture of Brega and the expected taking of Ajdabiya, the Khamis Brigade could race south of the Djebel Akhdar to Tobruk, cutting off Benghazi and securing the Egyptian border. Gaddafi can then sit back and starve Benghazi into submission. One can only assume that the National Libyan Council is deliberately holding back its regular/special forces for the defence of Benghazi.

The opposition and the international community must hope that Gaddafi's counter-attacks lose momentum, otherwise the rising will have been for nothing. All eyes are now on Benghazi.

Anthony Tucker-Jones is author of "The Rise of Militant Islam".