America officially closed a costly war that raged for more than nine years, killed some 4500 U.S. service members and dried out hundreds of billions from the United States Treasury.

The figures exclude the greater number of civilian contractors who perished due to countless attacks by Iraqi insurgents and the 100,000 civilians, more if the Iraq Body Count is to be believed, who were caught in the crossfire as campaigns to harass U.S troops increased and sectarian clashes surged during the height of the conflict.

On Sunday morning, the last of the U.S. troops motored into neighbouring Kuwait, where majority of them, according to the Associated Press (AP), would be prepped for a long-flight home just in time for the holidays.

But not everyone will take the flight home as the Pentagon, AP said, had decided to keep a considerable number of military presence that could quickly react to any form of unforeseen events.

Those events were actually more of fears that experts said could erupt as soon as the last U.S soldiers exit from Iraq.

The likelihood of returning to the violent period where hundreds were being maimed or killed everyday was not ruled out by observers as attacks spiked in the run up to America's full withdrawal.

With the U.S. troops out of the picture, experts said political infighting between Sunnis and Shiites could further spark instability and shake the already unstable government, which keeps a mere semblance of governance that functions on endless compromises.

Security experts also warned that al Qaida elements, even with the demise of Osama bin Laden, simply wait in the sidelines to exploit any situation that could favour their agenda.

America's departure was somewhat hasty as U.S. and Iraqi officials were unable to reach an agreement that would have allowed considerable number of U.S. troops to remain for purpose of further training the Iraqi security forces.

Baghdad balked at the idea of proving a blanket of immunity to U.S. security personnel, which Washington insisted as one of the bases for a deal to be struck, with its collapse triggering the accelerated pull out.

Nonetheless, America has indicated that it plans to still make its presence felt in the country as hundreds of troops and security contractors will be left behind to guard the sprawling U.S. Embassy constructed in the former Green Zone.

In a meeting with Iraqi Prime Minister Nouri al-Maliki last week, U.S. President Barack Obama had pledged that he remains committed in establishing a deeper relationship with Iraq, in accordance with America's goal of keeping a strong military presence in the region.

Overall, the success of the Iraqi Mission, Obama said, is best represented by the better future that lies ahead for the Iraqis.

"I would describe our troops as having succeeded in the mission of giving to the Iraqis their country in a way that gives them a chance for a successful future," Obama was reported by ABC News as saying.