Libya: How rebels have resisted pro-Gaddafi forces
In the past days, many have been puzzled as to how poorly-equipped and divided opposition groups have repelled a tide of Col Muammar Gaddafi's special forces, bombing raids and artillery-backed offensives, both around Tripoli and in the east.
The units that have decisively peeled away from the regime were precisely those that Col Gaddafi, anticipating disloyalty, had hollowed out over the decades - more so after a 1993 coup attempt, when elements of the Libyan army failed in their assassination bid.
So why is Col Gaddafi unable to translate his numerical and material superiority into a decisive blow?
It is hard to get any full picture of what is happening on the ground in Libya, not least because each party has incentives to project an image of success.
Some battles may be no more than light skirmishes, and accurate numbers of troops are impossible to obtain.
But some clues that can be offered from afar are drawn from the logic of military strategy.
The celebrated Prussian theorist of war, Carl von Clausewitz, made two important observations in his 19th Century classic, On War.
First, he argued that "defence is the stronger form of waging war". Fundamentally, it is easier to hold ground than to take it.
Even in the opposition-held cities close to government-held Tripoli - Zawiya and Misrata - wave after wave of co-ordinated government offensives were blunted by hastily organised rebels.
The urban backdrop appears to have afforded even greater advantages to the rebels. Home-made bombs could be dropped from roofs. Attackers were channelled through particular access points, so defenders could prepare fortifications and concentrate their forces.
Second, armies rely on "lines of communication" - paths by which attacking forces are linked to a supply base. Clausewitz argued that these lines become stretched as attackers move forwards, degrading the equipment and morale of troops.
In the strategic oil city of Brega, where the government was defeated in a key battle last week, Col Gaddafi's forces had advanced several hundred kilometres from the town of Sirte. By contrast, opposition reinforcements from Ajdabiya had a much shorter distance to traverse.
It is important to note that these points apply to regime and rebels alike. Though the government's power projection into the east may be ineffectual, the disorganised rebel armies have equally little hope of moving thousands of semi-amateur soldiers 500 miles (805km) westwards across punishing terrain.
A sweeping assault of the kind that Germany's Afrika Korps conducted on this soil during its World War II campaign is not yet on the cards, despite the rebels' bravado.
Third, what military analysts call the "correlation of forces" is not as lopsided as may appear.
The opposition are no longer unarmed protesters. The equipment that was rushed to Brega included anti-aircraft weaponry of the sort that has so far protected Benghazi from government jets.
In Ajdabiya, opposition forces were in possession of tanks from defecting army units, and wielded shoulder-launched missiles.
These are far less sophisticated than the equivalent weaponry available to the government, and probably lack trained users. But they afford some protection to the rebel armies.
It is true that the opposition, divided by tribal loyalties and political judgment, has nothing approaching a unified military command. But the battle for Brega demonstrated the impressive ability of small, disparate units to spontaneously mount a defence.
Those senior officers who have defected are focal points for military organisation, and could gradually fashion a more coherent system of command and control. That has been the pattern in civil wars of the past.
Fourth, and finally, air power is less potent than sometimes supposed. Though Col Gaddafi remains able and willing to inflict severe casualties on both rebels and non-combatants - missiles were fired at the victorious defenders in Brega - he is not easily able to use his aerial firepower to further his strategic aims.
Persistent but inaccurate bombing raids on the arms depot at Ajdabiya have accomplished little. Helicopter gunships would be more accurate, but also more vulnerable to ground fire.
Of course, massed opposition troops in open terrain would be at much greater risk than urban or concealed targets.
This only underscores the difficulties faced by hemmed-in rebels who wish to strike at Tripoli in the absence of a no-fly zone.
Presently, this burgeoning civil war is finely balanced. Col Gaddafi retains a stream of oil income and the loyalty of elite brigades, and he will have been heartened by US defence secretary Robert Gates' strong caution last Wednesday against military intervention.
At the same time, Col Gaddafi's grip on Tripoli is fragile, he has failed to hold oil installations in the east, and sanctions will inevitably be ratcheted up as the stalemate is prolonged. The denouement of Libya's revolution still lies many weeks over the horizon.
Shashank Joshi is an Associate Fellow at the Royal United Services Institute (RUSI), a defence think-tank in London, and a doctoral student of international relations at Harvard University.