"A measure of security is certainly required, LEJ. I'll agree with that. I think it would be better if such security was provided by local troops, rather than foreign troops."

So you have a country that has known nothing but strife and full scale civil war for 22 years, it has no Government, no administration and has been declared a "failed State" by the United Nations.

With the agreement of the tribal leaders and other representatives of the Afghan people The UN reach agreement to assist in the reconstruction of Afghanistan at Bonn In Germany in December 2001.

The United Nations Assistance Mission to Afghanistan is formed (UNAMA), everybody involved realise that this effort must be protected and that job the United Nations gives to NATO, and the International Security Assistance Force is formed under NATO leadership. Their tasks as detailed in their mission statement and in the mandate given them by the United Nations Security Council also tasks them with the job of training and making ready the new Afghan Security Forces. In that way the job could be handed over to local troops.

The Mission Statement and Mandate of NATO-ISAF does not mention Osama bin Laden; Al-Qaeda or the Taleban.

"The USA ostensibly went into Afghanistan in 2001 to destroy Al Queda camps and capture or kill Osama Bin Laden and other Al Queda commanders."

This was a completely separate force US-Operation Enduring Freedom-Afghanistan and it was mandated for precisely that purpose by the United Nations. They have no role in the reconstruction of Afghanistan their job is to make sure that neither Al-Qaeda or the Taliban re-establish themselves as a power in Afghanistan until after such time that the Afghan Government can stand on their own feet.

"How did that morph into "nation-building"? And why?"

The US-OEF-A mission has not morphed into "nation building" or anything else you still have two distinct military missions operating inside Afghanistan.

US-Operation Enduring Freedom Forces operate as part of US CenCom under the command of US General David Petraeus, their job is best described as Counter-Terrorist.

ISAF operate as a NATO formation under the command of US General Stanley McChrystal, their job is best described as Counter-Insurgency.

UNAMA is the United Nations organisation tasked with "nation building".