There are reports that the Taliban offered unconditional surrender in December 2001.

This is so shocking that I can't accept it as unquestioned truth without further substantiation. Anand Gopal heard the story in Afghanistan some time after 2008. That was plenty of time for distortion to set in. I took a quick look at his book, but that part doesn't say where he got the information; can anyone tell me whether that is stated elsewhere in the book?

I won't accept it as unquestioned truth, but I won't say it must be false, either.

Dubya had previously rejected an offer by the Taliban to surrender Osama bin Laden and break off with al-Qa'ida. Accepting that offer would have satisfied the supposed purpose for the invasion of Afghanistan.