This incident reminds me of some research I came across while working on my junior theme. During the Vietnam War, there were over 500 incidents of "fragging," an episode in which U.S. soldiers murdered their own officers. Although a different situation, "the stress of war" was regarded as the main factor behind these episodes.
However, there is a big difference between the Afghanistan War and the Vietnam War; The Vietnam war had a draft. To me, this makes the incidents with the Vietnam soldiers less surprising because I would expect that a greater number of soldiers were fighting against their will--making them more susceptible to well, going crazy.
But if incidents like Bales' are still occurring, what does that suggest about our military today? With an absence of a draft is there the same amount of stress amongst soldiers? Maybe this war has just dragged on too long?