When President Obama began campaigning for office, as to national security policy, he could have hardly been more clear as to his premises, agree with them or not, or what mix of agreements and disagreements one could take from that.
The premises were totally stated upfront.
As to the premises that matter in the context of war and peace, President Obama promised to withdraw from Iraq, as to achieving the second premise, which was to wage war more effectively on Al Qaeda in Afghanistan and in Pakistan too.
That is exactly what he had done. We don't have troops in Iraq, but only contractors in a large embassy complex. One could argue if that was optimal, but one can't argue that he didn't do what he told the Left, his supposed supporters, what he said he would do.
As to Afghanistan, the President clearly stated long before he took office that he thought the real problem after 9/11 was in Afghanistan, not Iraq.
Reasonable people could disagree about how to approach this problem, as some would see Great Power proxy wars as more important, but, one cannot deny that the President did exactly what he told his supporters before the election he would do, which was intensify American-NATO efforts in Afghanistan.
Moreover, as to this weird betrayal on the Left, and this is from someone who's pretty much a Republican, after Bin Laden was killed, President Obama announced a winding down of the war in Afghanistan.
Some people in the military thought that was a little premature, others thought that it would force certain issues front and center to be solved, and there isn't really a great way to tell who's right.
As to what the President has achieved in Afghanistan, through of course the efforts of the U.S. Armed Forces, he's given the people of Afghanistan a chance to not be a menace to eacgh other or their neighbors and peace in general, and a menace of Afghanistan as a failed state was the one clear implication of 9/11.
Moreover, if the President succeeds in drawing down forces over the next two years in a responsible fashion, he forces the regime to bargain over its future with who will be part of that future, to some extent the Taliban and other regional actors, in which the interests in play are really obvious.
As to the interests, Afghanistan has long been understood to have vast mineral wealth, iron ore in particular, if also Rare Earth minerals. India and China are growing rapidly, and need such minerals, just as they need the oil and gas from Central Asia too, just like the world needs the Rare Earth minerals of Afghanistan present in large quantities.
The cynics make this out to be some sort of neo-imperialist project, and it is to a point, but, it's also necessary for Afghanistan to have a viable state.
Without a revenue source, opium is it for the Afghan state, hardly in our interests here to be the case.
But as to all this complaining on the Left, give the man a chance.
Many in the professional military wouldn't have wished to totally leave Iraq, at like two brigades, but, that's worked out better than expected. The same thing could be said as to Afghanistan and withdrawals, but, we are lowering our presence both places, so why does the Left eat their own President, when he's doing what he said he would do?