can do vs. must do?

"As I’m sure many already know this year Afghanistan has seen the worst violence since we first came in 2001. There have been rough times with poppy cultivation exploding out of control, struggling corruption in the government, and an ongoing insurgency that still poses a real threat…as seen the by recent battle to recapture Musa Qala in Helmand province from the the Taliban who had control of the area since February. However, Iraq still remains a bigger priority in the eyes of American commanders…rightly so.
Recently there has been news of Sec. of Defense Gates urging our NATO allies to offer more troops to the fight in Afghanistan, and congressmen from the House Armed Services Committee have been suggesting we increase the US presence there. Apparently though, according to the Chairman of the Joint Chiefs of Staff, WE can’t offer any more troops from our military toAfghanistan because it is a “matter of resources, of capacity” and “In Afghanistan, we do what we can, In Iraq, we do what we must.” Not exactly comforting words to all the US troops over here, sure does make me feel all warm and fuzzy."
Afghan Vacation