The part that stood out to me in the second half of Jarhead the most came at the bottom of page 183 when Swofford revealls what he later learned about the anti-chemical-warfare pills they had all been taking. He discovers that they were approved for a very strictly limited number of doses. He thinks that they took way in excess of the approved amount but explains the reasonning behind it. That if 21 pills will keep them from dying, then 42 is better, and 63 is golden. The side effects later on are unimportant because they just want to believe that they can actually do something that will keep them alive.
While this is just another example of how the government will lie to you and change the story as they see fit, it brings into understandable terms at what the pills were most likely approved for. It's probable that in the modern world of medicine that they did not know whether or not the pills would really prevent death or disease form chemical attacks but just that they would give soldiers hope and the belief that they would be okay if they fell under chemical attack; a sick sort of placebo effect.