As the civil war in Libya escalates, Barack Obama is faced with more and more scrutiny over the United States' military campaign in the African nation.

Obama was recently asked to defend the US presence in Libya, after House Speaker John Boehner (R-Ohio) said that the President had violated the War Powers Act by not getting congressional approval for the campaign.

But why exactly is the United States in Libya in the first place?

The US does, of course. want to protect oppressed people around the globe. And it wants to promote democracy and equality when the chance arises.

But Council on Foreign Relations senior fellow for defense policy Stephen Biddle says that the president was really pressured by NATO allies France and Germany, both of whom had more desire to support the Libyan rebels.

The European nations both have significant a troop presence in Afghanistan and Biddle sees the Libya operation as a form of payback. Obama might have agreed to help in Africa to keep his NATO allies happy.

Both Germany and France each currently have more than 4000 soldiers in Afghanistan, although French President Nicholas Sarkozy announced Wednesday that he too would withdraw troops by 2011.

Given the progress we have seen [in Afghanistan], France will begin a gradual withdrawal of reinforcement troops sent to Afghanistan, in a proportional manner and in a calendar comparable to the withdrawal of American reinforcements, Sarkozy's office said in a statement.

Additionally, the end result of the Libyan war will have an effect on oil prices around the world, but Europe has a more vested interest in the North African nation's oil reserves. Italy gets a significant percentage of its energy from Libya, which might explain why they have been on the side of Gaddafi in the past.

The US is exposed both militarily and economically by the NATO mission in Libya, which makes Biddle think that it could lead to a drastic change in NATO's role in world politics.

NATO has benefits to the United States, Biddle said, but the costs of membership are becoming clearer to Americans.

One of these costs is what Biddle calls the entrapment risk, which is getting caught in an ongoing war for little domestic reason, such as in Libya. He foresees a shrinking of NATO in the near future, where the benefits for member nations will weigh more closely to the costs.

US Secretary of Defense Robert Gates said as much during a speech delivered in Brussels, Belgium last Friday.

For Gates, the NATO mission in Libya has made it painfully clear that similar shortcomings - in capability and will -- have the potential to jeopardize the alliance's ability to conduct an integrated, effective and sustained air-sea campaign.

Gates pointed out that all the member nations voted in favor of entering the Libya conflict, but fewer than half of those states have contributed to the mission in any way, and fewer than a third have been willing to participate in the strike mission. 

Frankly, many of those allies sitting on the sidelines do so not because they do not want to participate, but simply because they can't. The military capabilities simply aren't there, he said in the speech.

He feels that the United States and other economically powerful nations take an unfair amount of the burden while smaller members just get the benefits without the sacrifice. He noted that NATO has depended on the United States for bombing targeting equipment and specialists.

In the past, I've worried openly about NATO turning into a two-tiered alliance: Between members who specialize in 'soft' humanitarian, development, peacekeeping, and talking tasks, and those conducting the 'hard' combat missions. Between those willing and able to pay the price and bear the burdens of alliance commitments, and those who enjoy the benefits of NATO membership -- be they security guarantees or headquarters billets - but don't want to share the risks and the costs.  This is no longer a hypothetical worry. We are there today.  And it is unacceptable.