What does the occupation of Tripoli by Libyan rebel forces tell us? Shadi Hamid, director of research at the Brookings Doha Center, said Libya confirms that the role of external actors (in this case, the United States and Europe) can still be decisive in the Arab struggle for freedom.

First, some Libyans that joined Al-Qaida and were then locked up by the United States at Guantanamo Bay joined the rebel forces after release and set up their own semi-independent military groups.

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The US knew this. But because overthrowing the Muammar Gadhafi government is a task of top priority for Washington, the US did not demand the Libyan National Transitional Council (NTC) disarm these fighters. Even though it was reported that Abdel Fattah Younes, the rebel commander, was killed by these people, the US and other Western countries have taken the stance that "yesterday's enemy" are "today's allies".

Second, and perhaps more importantly, the US has assumed a major role in NATO's military strikes against the Gadhafi regime.

At the beginning of NATO's military operations against Libya, the US took command and the first batch of Tomahawk missiles were launched from a US warship. Before long, the US returned military command to NATO with a Canadian general in charge. As a result, NATO's own "problem" was clearly revealed.

As former US defense secretary Robert Gates pointed out, NATO is facing great "budget pressure" in the post-Cold War era. The US covered about 50 percent of NATO's expenditure during the Cold War. However, after the end of the Cold War, while the European security situation eased up, the US' share of NATO's costs rose to 75 percent.

Now, because of the Afghan and Iraq wars, coupled with the 2008 financial crisis, the US has had to heavily cut its military budget and the US asked its NATO allies to share more of the burden.

However, European countries are also facing a financial crisis and budget pressures, and they declined Gates' request.

Gates complained that the mightiest military alliance in history was only 11 weeks into an operation against a poorly armed regime in a sparsely populated country - yet many allies were beginning to run short of munitions, requiring the US, once more, to make up the difference.

So the US has had to "quietly" assume the major burden of NATO's military operations against Libya, although it did not "reclaim" command and only participates in non-direct military actions, including surveillance and reconnaissance, which depend more on electronic means.

In the face of intense domestic debate over raising the debt ceiling and cutting the budget, the US government doesn't want to play with fire by publicly claiming that it bears the main responsibility for NATO's military operations in Libya.

But the role of "non-direct military operations" in toppling the Gadhafi regime cannot be underestimated.