On Thursday, the U.N. Security Council authorized its members to take "all necessary measures"--including a no-fly zone and possibly a no-drive zone-- to prevent Libyan leader Muammar Qaddafi from attacking civilians by air, land, and sea. On Friday, President Obama announced that the U.S. would not deploy ground troops in Libya and that it would use force with only the limited goal of protecting Libyan civilians.

But what does that mean? What is the U.S.--already stretched thin by the wars in Iraq and Afghanistan--really commiting to? There are four primary dimensions to the debate:

The Resolution's Meaning

Ray Takeyh at the Council on Foreign Relations claims that the Security Council resolution is about more than a no-fly zone. The U.S., he says, is now "morally and practically obligated to the survival and viability of the anti-Qaddafi insurgency."

But former ambassador Marc Ginsberg's not sure what the resolution means: "Is its goal to buy breathing room for the opposition to regroup and rearm in order to swing the attack back across the desert to Tripoli under protective allied air cover? Or is it merely a license to freeze the military equation to protect the opposition in Benghazi and impose a 'painful stalemate' on Qaddafi for an indefinite duration with the hope that other UN-sponsored sanctions will grind him down and cause more tribes to revolt against him?"

The Logistics

National Journal's Yochi Dreazen explains that while the U.S. took the lead in enforcing no-fly zones in Iraq and Yugoslavia, Obama now only wants the U.S. to enable European and Arab nations to enforce a no-fly zone, though U.S. warplanes will probably be needed if the Qaddafi regime abandons the ceasefire it announced on Friday morning.

The BBC's Caroline Wyatt, meanwhile, predicts the French, who have already stuck their necks out by recognizing the Libyan rebels diplomatically, may spearhead the international military effort.  And Yahoo's Laura Rozen is reporting that the U.S. won't send airplanes into Libya and will only support the no-fly zone diplomatically.

The Tactics

In granting members broad authority to protect civilians, Cooper says, the U.N. resolution has enabled the U.S. and its allies to not only "try to force Qaddafi’s attack helicopters and jet fighters out of the skies," but also, if need be, to "target his tanks, armored personnel carriers, and infantry. That, in turn, suggests that a Libyan no-fly zone could quickly turn into something far larger, and far more dangerous, for both sides."

The End Game

If Qaddafi "is deposed and the state collapses into tribal warfare," muses The Washington Post's Ezra Klein, "does our pledge to resist ground troops trump our pledge to protect civilians? Or will it be the other way around?" And what if the rebels cannot defeat Qaddafi and he remains in power, at least in the western half of the country? "The last thing we need to be doing is providing air cover for an extended, bloody military stalemate that drags on and on," states Ginsberg.

The Big-Picture Rationale

The Atlantic's Andrew Sullivan calls out the Obama administration for justifying the Libyan intervention because the uprising is threatening regional stability: "The president argued that the ghastly violence in Libya is destabilizing the region, and threatening world peace. Really? More than Qaddafi's meddling throughout Africa for years? More than the brutal repression in Iran? And even if it is destabilizing, Libya is not, according to the Obama administration itself, a 'vital national interest.'"

"Every year," Klein adds, "one million people die from malaria. About three million children die, either directly or indirectly, due to hunger. There is much we could due to help the world if we were willing. The question that needs to be asked is: Why this? ... What I mainly heard in Obama’s remarks were statements about human rights--fair points all, but applied so inconsistently that they always make me skeptical. Will we take on Yemen, next?"

"Why not intervene in Burma or Yemen or elsewhere?" responds The New Republic's Jonathan Chait. "For various political, geographic, and military reasons, the United States has the chance to prevent slaughter in Libya at reasonable cost, and does not have the chance to do so in Burma."