US military officials made it clear that the gains Libyan rebels made in the past few days could be reversible. They were right. Contrary to the boasts from the rebels about capturing Gadhafi’s hometown of Sirte, they were in fact repelled there.

Rebel forces’ westward charge was repulsed on Monday by a barrage of tank and artillery fire from forces guarding one of Col. Muammar el-Qaddafi’s most crucial bastions of support, while the American military warned on Monday that the insurgents’ rapid advances could quickly be reversed without continued coalition air support.

“The regime still vastly overmatches opposition forces militarily,” Gen. Carter F. Ham, the ranking American in the coalition operation, warned in an e-mail on Monday. “The regime possesses the capability to roll them back very quickly. Coalition air power is the major reason that has not happened.”

Which just underscores how this coalition operation is an offensive mission, becoming the rebel air force in a Libyan civil war. And still it’s not been enough to force the rebels into any territory they hadn’t already controlled during this conflict. It certainly won’t be enough for Tripoli and it hasn’t been enough for Sirte.

The coalition hopes that mass defections of the government troops ensue as the rebels gain territory. That would provide the rebels with needed additional numbers, as well as actual trained forces. But so far, that has not happened in any concentrated fashion. In fact, the Times article explains that pro-Gadhafi troops fooled the rebels outside of Bin Jawad by waving white flags, drawing them closer before opening fire. There’s more from the Guardian.

Meanwhile, Italy has prepared an escape route for Gadhafi which would put him beyond the jurisdiction of the International Criminal Court while in exile. And US officials, including even John McCain, are prepared to accept that. But there’s no indication that Gadhafi wants any part of the escape. His plan is clearly to fight to the death.

This brings us to another unanswered question of the Obama speech last night: what happens in a stalemate? I certainly hope it doesn’t happened, but you don’t have the luxury of time-limiting a civil war, and not preparing for all contingencies. I suppose you could partition the country, but I don’t see either side agreeing to that. The intervention has been sold as a quick way to align interests and values, but what if it’s not so quick? What if there’s no real solution under the current mandate and given how far the coalition, including the US, is willing to go?

This is the usual time when mission creep raises its ugly head.

UPDATE: And just like that, Adm. James Stavridis, the top military officer of NATO, floated NATO ground troops for Libya.

During a Senate hearing on Tuesday, Sen. Jack Reed of Rhode Island asked Adm. James Stavridis about NATO putting forces into “post-Gadhafi” Libya to make sure the country doesn’t fall apart. Stavridis said he “wouldn’t say NATO’s considering it yet.” But because of NATO’s history of putting peacekeepers in the Balkans — as pictured above — “the possibility of a stabilization regime exists.”

So welcome to a new possible “endgame” for Libya. Western troops patrolling Libya’s cities during a a shaky transition after Moammar Gadhafi’s regime has fallen, however that’s supposed to happen. Thousands of NATO troops patrolled Bosnia and Kosovo’s tense streets for years. And Iraq and Afghanistan taught the U.S. and NATO very dearly that fierce insurgent conflict can follow the end of a brutal regime. In fact, it’s the moments after the regime falls that can be the most dangerous of all — especially if well-intentioned foreign troops become an object of local resentment.

Stavridis added that we have no idea who the Libyan rebels are.