By William Maclean
LONDON (Reuters) - The fortified Tripoli compound attacked by Libyan rebels Tuesday is the seat of Muammar Gaddafi's political power and the principal base of loyalist fighters trying to rescue his 42-year-old rule.
Analysts say Gaddafi loyalist fighters confronted with an influx of rebels since the weekend have sought to use his Bab al-Azizyah bastion as a springboard from which to carve out a loyalist zone and chip away at rebel control of adjoining neighborhoods.
The encampment is believed to sit atop a network of tunnels and bunkers that lead to adjoining districts, including possibly a subterranean route to the coast.
But the tunnel networks are not the loyalist militiamen's only card: Gaddafi's fighters have an intimate knowledge of the city and many are believed to have a greater degree of military training than their opposition guerrilla opponents.
"This is Gaddafi's Pentagon," said Noman Benotman, a senior analyst at the British think tank Quilliam and a former Libyan Islamist opposition guerrilla commander.
He said tunnels forking out from the complex to nearby districts gave his fighters precious access to supplies.
"Based in Bab al-Azizyah, Gaddafi's force want to create chaos inside Tripoli and carve it up into rival militia zones, just like Beirut in the Lebanese civil war," said Benotman, who is also an associate of former Libyan spy chief Moussa Koussa
"By sending a message that 'there will be no peace without us' his aim is to force his inclusion in talks on a political negotiation."
Long the seat of Gaddafi's power as well as his main Tripoli home, the barracks may well be the final battleground of Libya's war. Even if Gaddafi is not there, its loss would inflict a potentially crippling symbolic defeat.
If Gaddafi is at the six sq-km (2.3 sq mi) base, located south of Tripoli at the northern end of the Airport Highway, there is a fair chance he is in a tunnel under it rather than in a fortified room above ground.
The compound has often been targeted by NATO air strikes, but it is still defended by tanks and snipers, a fact that suggests Gaddafi or at least some key aides are nearby.
Al Arabiya news channel said rebel forces had attacked the gates of the compound Tuesday as NATO warplanes flew low overhead. Sky Television said smoke could be seen billowing from the compound following a NATO attack.
COMPOUND WALLS CAN BE BREACHED "FROM THE AIR"
The site is normally dotted with tents, residential buildings, security encampments, and the cratered remains of a house bombed by U.S. warplanes in 1986 and kept in ruins as a memorial. A communications center, attacked months ago by NATO, sits on an adjoining plot.
Umar al-Hariri, a military official of the rebel Libyan National Transitional Council, told Al-Sharq al-Awsat newspaper in June that the barracks were linked to underground tunnels up to 30 km (20 miles) long, some of which led to the sea.
Hariri said that for rebel fighters attacking the compound it was just as important for NATO to breach the meter-thick, olive-green walls as to access the tunnels underneath.
"I met NATO at one time and told them that the most important thing they should strike are the walls of Bab al-Aziziyah because their thickness is one meter and they cannot be penetrated by a tank or gun. There must be a penetration from the air," he was quoted as saying.
He put the height of the walls at four meters.
Built in the era of King Idris, overthrown by Gaddafi in the 1969 putsch that brought him to power, the site was reinforced in the 1980s using an array of foreign contractors.
FOREIGN COMPANIES CONSULTED
Analysts say Western intelligence services will have long ago sought to question any foreign companies that helped build tunnels under the site, to learn how to attack the compound.
From a rebel and Western perspective, that information is growing more valuable by the hour.
Jon Marks, chairman of Britain's Cross Border Information risk consultancy and information service, said he suspected Western governments will have asked foreign companies that helped Gaddafi build his Great Man Made River project for any information about the tunnels under Tripoli, on the assumption some may have helped build them.
The Man Made River project sends water from wells in the Sahara desert to coastal communities along a 4,000 km (300 miles)-long network of pipelines.
"The governments will be asking the companies for a debrief," he said, adding the Tripoli tunnels "may have been done as a side order from the Man Made River work."
(Reporting by William Maclean)