Sorry, that is a pretty lame reason to put our soldiers at risk. As has been proven over time, the reasons for entering the war were proven false. You could say the same thing for many other countries and we have not invaded them.
We were in a state of war with Iraq already. Our troops were stuck in Saudi Arabia for 10 years in a siege against Iraq. Were we just to pull the troops out and let the Saudis and Kuwaitis deal with the mess. Let Iran have its way? If we did win Afghanistan first would you move our troops back into Saudi Arabia were they were before. What do you do with Iraq?
I continue to believe Obama is either incredibly stupid or he's willingly doing things to wreck this country (and I'm no hard-core conspiracy guy). Why else would you announce (a) more troops and a surge and then (b) the timetable for a troop withdrawal? That certainly makes planning easy for the enemy. Just lay low, do some limited/random terrorist attacks, build up your forces and manpower and do your own surge as we're leaving. We've done some dumb things in Vietnam and Iraq, but I'm not sure if we've ever telegraphed our strategy like that...