Spencer Ackerman wants a case for not sending more troops to Afghanistan. Specifically, he wants to know why the US military is keeping a brigade of Marines in Kuwait as a reserve. Well. The first point is that there is a very good reason to have a reserve force at the far end of the main supply route into Iraq. With the British force outside Basra, this adds up to a considerable strike force for use in the event that someone decides it's time to cut Highway 8. For the someone, try here.
But there are good reasons to think that we should not be sending more troops into Afghanistan. For a start, have a read of this. The Taliban, it is argued, use "kinetic operations" - i.e. force - in support of "information operations" - i.e. propaganda, rather than the other way round. (Anyone else remember the Armalite and the Ballot Box at this point?) They are therefore keen for the Afghan government to be seen as a cruel authority with foreign tanks and planes, bent on bombing weddings and destroying poppy fields.
Secondly, the more large army units that go, the more bases will be built, the more money spent on directly military purposes, the more trucks will be involved in road accidents. More teachers will quit their jobs to be paid more money driving white Land Cruisers. The whole force will be even more dependent on the road from Karachi; this is not a good thing.
Thirdly, pouring more resources in might be a way to avoid changing policy. Consider this article by Antonio Giustozzi. Giustozzi's point is that whatever the available resources, the Afghan army is never going to be the answer because of its internal contradictions. It is being built as an instrument of Tajik power, and as a barracks army for use anywhere in the country. Worse still, it has an explicit policy of sending northerners to Pashtun country; which is something like the opposite of counterinsurgency. But because it's "the army", it's likely to be the preferred partner of an enlarged ISAF.
Arguably, more Western (or Eastern, for that matter) combat units are the last thing Afghanistan needs. Nor anybody else. Send more advisors; send money; revive the auxiliary police force; insist on a political solution. But no more wedding raids, hesco barriers, or monster trucks.