This morning, on the 100th day of NATO operations in Libya, an opposition spokesman shared some exciting news with the AP: the rebels, having wrested control of eastern Libya and parts of western Libya, including the Nafusa mountains, from Muammar Qaddafi's forces, had now advanced to within 50 miles of Tripoli, with heavy fighting cropping up in the mountain town of Bir al-Ghanam. But before we declare Qaddafi cornered and defeated, it's important to note that the rebels have closed in on Tripoli before, only to be driven back east later by the regime. Let's look briefly at the two previous instances:

Tripoli Advance #1: In late February, only weeks after Libya's uprising erupted, the rebels seized coastal cities in the east and even the western city of Misurata. After the rebels repelled a Qaddafi attack in Zawiya, only 30 miles from Tripoli, an opposition leader drew a map of rebel-held territory near Tripoli and boasted to The New York Times, "It is only a matter of days." But, as The New Yorker's Jon Lee Anderson notes, the rebels' "ill-planned, euphoric advance westward" turned into a "panicked retreat" eastward when Libyan forces launched a counterattack from Qaddafi's stronghold of Surt in early March. The rebels--a "leaderless rabble of university students, mechanics, shopkeepers, and Army reservists"--found themselves "bloodied and outgunned." As Qaddafi's forces closed in on the rebel stronghold of Benghazi, the U.N. authorized a no-fly zone.

Tripoli Advance #2: The rebels, buoyed by coalition airstrikes, once again advanced toward Qaddafi's birthplace of Surt in late March, prompting The Independent to observe that "the milestones on the road to Tripoli are falling" as the shift in momentum grew "palpable" and the regime's soldiers contended with "overwhelming odds." But that feeling was short-lived. Days later, the rebels beat a hasty retreat to Ajdabiya in the east in the face of artillery and rocket attacks. The fighting has since devolved into what many analysts consider a stalemate.

So might this week's advance prove more successful than the previous two? The AP notes that geography could play an important role. While most of the fighting in recent months has centered on front lines east of Tripoli, the agency notes, a "push by rebels from the Nafusa mountains could force Qaddafi to commit more troops to the southern and western approaches to the capital." Indeed, the rebels battling in Bir al-Ghanam are now only 18 miles south of Zawiya, which, if captured, would allow them to approach Tripoli from the west and cut off supply lines from Tunisia. The Los Angeles Times adds that communication between the rebels has improved. In recent weeks, the paper explains, rebel committees in the Nafusa mountains "have begun to coordinate more closely with one another and with their allies in the eastern city of Benghazi."

Still, The New York Times points out that rebel successes are confined to the mountain region, where the rebels "have used their knowledge of the terrain and the sympathies of much of the local population to expand their territory as the fighting around Benghazi to the east and Misurata on the central coast has moved toward a stalemate." Al Jazeera observes that the rebel army still consists of "ill-equipped irregulars and defectors" while the BBC's Mark Doyle doesn't think we should expect Qaddafi's departure anytime soon despite the opposition consolidation of power in the mountains. So, in other words, don't hold your breath for an imminent storming of Tripoli.