That's the first thing that popped into my head when I read this.
Murtha said combat stress prompted the Marines’ alleged rampage.
“It’s a very serious incident, unfortunately. It shows the tremendous pressure that these guys are under every day when they’re out in combat,” he said. “One man was killed with an [improvised explosive device] and after that they actually went into the houses and killed women and children.”
This is why war should not be glibly wished for nor engaged by leaders without the soberest of intentions and should always have clear objectives and timetables. Colin Powell understood this (or used to) in formenting the Powell Doctrine.
(Of course Powell had also helped to try and cover-up the Mai Lai massacre as a young army officer so his judgement may not be the best point of refererence.)