Frank Rich of the NYT believes that a military build-up can and must be resisted by President Obama. Of course, if he does he will be bombarded with leaks to the press from the military and accused of "defeatism" by the neo-cons. But Kennedy refused a military build-up in Vietnam and kept the U.S. in an advisory role.
Then came LBJ and what Johnson came to call the most disastrous policy of his presidency: full-scale war in Vietnam. This decision ruined the Great Society and LBJ's presidency.
While I think the right-wing outcry would be furious, the public generally would likely respect Obama's deicsion to keep the troop levels low.
This may be the most important decision of the Obama administration.