Max Boot argues that the U.S. should station large numbers of troops in Afghanistan indefinitely, then undermines his argument at the end of his op-ed:
It is hard to imagine how anyone in the Obama administration could conclude that a force of just 6,000 personnel would be sufficient after 2014 when, even with 68,000 troops today, the United States cannot prevent the Taliban and Haqqanis from operating openly an hour’s drive from Kabul. Such a precipitous drawdown vastly increases the risk of a Taliban takeover. [Emphasis mine.]
It's obvious to even the war's die-hard supporters that there is no sufficient American force available to keep the Taliban and Haqqani militants from threatening Afghanistan. So why subject an arbitrary number to an indefinite stay in Afghanistan?