In general, draftees during the Vietnam War were put into the army, but the Department of Defense always had the prerogative to place anyone wherever they wanted. The fact that one could select something other than the army if one enlisted was an incentive to avoid the draft. One could for example, sign up for the Air Force or Navy - or even the Coast Guard - and could hope, consequently, to avoid being sent to Vietnam. That strategy didn't always work out, and the price of the choice was a longer enlistment: the draft was for 2 years while enlistment was usually for 4 years (and Coast Guard frequently required 6 years). And of course, Navy and Coast Guard patrols in the Mekong Delta and elsewhere could put a volunteer into serious danger, so that approach - if the goal was to avoid life-threatening situations - didn't always work.

Are you interested in any particular time period?

When I was drafted in 1971 in New Haven, CT there were about 40 guys in attendance. Once the physical exam was finished and all other issues attended to, we were seated on risers. One of the recruiters stood up and simply pointed to each guy in turn "Army, Army, Army, Marines."