If the US Army or whatever ,have not yet been able to devise a test,or series of tests,that can establish a recruit's psychological state of mind,reason for wanting to join up,and mental fitness to serve,then God help us all !!
             Having said that, there doesn't seem to be much point in joining the Armed Forces if you are NOT prepared to kill people,when you think about it ! During the Falklands War,here in Britain,a navy Chief Petty Officer was drafted to a warship bound for the South Atlantic war-zone,and refused to go!!----He said " That's not what I joined the navy for " !
          He was court-martialled, of course.