The elite Khamis Brigade was reputed to be the most loyal and powerful unit in Colonel Moammar Gadhafi's army. Personally commanded by one of his sons, the 10,000-man armoured brigade was said to be the best-equipped and most-feared force in his security apparatus.
Yet when Libyan rebels approached the brigade's main base on the outskirts of Tripoli on Sunday, the soldiers quickly surrendered. The city's supposedly impregnable defences were soon breached, and the rebels rolled in.
The collapse of the Khamis Brigade was symbolic of the fate of the Gadhafi regime itself: A façade that seemed formidable from the outside, but suddenly crumbled in the face of relentless military pressure. After months of stalemate, the end was astonishingly swift.
Analysts say the disintegration of the Gadhafi forces in Tripoli resulted from a combination of factors, including the fierce pounding of Western air strikes, tactical help from British and French special forces, surveillance intelligence from U.S. Predator drones, and a carefully planned encirclement operation by the rebels themselves, who approached Tripoli from multiple directions with the aid of sleeper cells inside the city.
But while the high-tech weaponry was useful, the key factor was the brittleness of the Gadhafi regime, which was unable to command the support of the Libyan people.
"Repressive regimes always rely on the fear factor, and their very strength is ironically their biggest weakness," said Barak Seener, a Middle East expert at the Royal United Services Institute in London.
He compared the Gadhafi collapse to the swift downfall of Iraqi dictator Saddam Hussein after the U.S.-led invasion in 2003. "They get their support from fear, and fear is very hollow. Loyalty due to fear can turn very quickly."
In Libya, the cumulative effect of months of NATO air strikes "demonstrated to the population why it was safe for them to come on board the rebellion," Mr. Seener said.
The surrender of the Khamis Brigade was significant in other ways too. The commanding officer of the brigade's base near Tripoli had for years remembered how his brother had been unjustly killed by the Gadhafi regime, reports say. Because of this, the officer was secretly loyal to the rebels. When the rebels arrived at the base, he surrendered almost immediately, giving an arsenal of weapons to the rebels and allowing the release of 400 political prisoners from a jail at the base.
Col. Gadhafi's failure to win the hearts and minds of the Libyan people was further exposed by the uprising of the sleeper cells – secret groups of rebel loyalists inside Tripoli who were armed with weapons smuggled into the city over a period of months.
On Saturday night, mosques across Tripoli broadcast a call for civilians to rise up against the regime. It was the signal for the sleeper cells to awaken, and soon they joined the rebel units that were advancing into the capital.
For months, the rebels had been bottled up in the deserts of eastern Libya, far from Tripoli. But during the past 10 days they made dramatic gains in the west and in the Nafusa mountains, just south of Tripoli. By the weekend, they were able to advance on the capital in a co-ordinated operation from three directions. They even managed to send 200 rebels into the Tripoli region by ship, bypassing Gadhafi strongholds to the east of the city.
Meanwhile, with the aid of British and French special forces inside Libya, the rebels became better organized and improved their command and control structures. The special forces provided logistical support, basic training and expertise for the rebels as they advanced.
At the same time, the NATO air strikes were becoming more precise and effective, with the aid of surveillance from Predator drones and rebel spotters on the ground. Since late April, the armed Predators have launched more than 90 attacks on targets in Libya. The United States sent two additional drones to the Libya conflict last week, reinforcing the intelligence-gathering capacity of NATO and the rebels.
Over the past five months, NATO warplanes have flown nearly 20,000 sorties, including nearly 7,500 strikes at Gadhafi targets, but the most significant may have been their 40 attacks on targets in Tripoli on Saturday and Sunday. By hitting the regime's defensive positions in the capital, they made it easier for the rebels to move forward. And as the Gadhafi forces came out to engage the advancing rebels in firefights, their positions came into view for the drones and the warplanes to attack.
The collapse of Col. Gadhafi's forces could be an inspiration to popular uprisings in Syria and elsewhere in the Middle East, Mr. Seener said. "The galvanizing effect is tremendous. It shows that the security apparatuses are not as robust as they had assumed."