http://www.telegraph.co.uk/men/thinking ... f-war.html
Perhaps no one group of soldiers better exemplifies the impetus for slang than the US troops who fought in Vietnam during the 60s and early 70s. Combat naturally fuels a resentment of authority and a dislike of regimentation, while fostering a strong sense of egalitarianism. In Vietnam, this was amplified by the large number of conscripted men in the US ranks, whose participation in a highly authoritarian and dangerous institution was strictly involuntary. The slang that they coined reflected their values of dissent against the inevitable. It was imaginative and largely unsentimental, blunt, and what it lacked in social graces it gained in irony and dry humour.
By George , I think he got it. Well... maybe "strictly involuntary" was a bit strong. Maybe there because they showed up for the bus when the draft notice told them they had been "selected" would have been closer to the truth.