What's the mission in Afghanistan?

"Thousands of U.S. troops originally destined for Iraq have deployed south of Afghanistan's capital in the first illustration of a new military focus on the increasingly difficult fight in the South Asian nation . . . President Barack Obama is expected to double the size of American troops in Afghanistan this year, as the country becomes one of his foreign policy priorities. There are some 70,000 foreign soldiers, including 33,000 U.S. troops . . ."

http://news.aol.com/article/us-troops-diverted-to-afghanistan/317153

Of course, everyone agrees that Afghanistan can't be conquered, pacified or taught democracy.

http://www.miamiherald.com/news/politics/AP/story/875199.html

So, why are we sending 60,000+ troops to Afghanistan?