Last month, National Guardsman Ryan G. Anderson was arrested and taken into custody at Fort Lewis, Wash., accused of attempting to provide information to the al Qaeda network. The arrest happened to fall on the two-year anniversary of the trial against ousted Serb. president Slobodan Milosevic. The confluence is not entirely unsymbolic. ...The attempts to sabotage the armed forces should not be catching us off guard. Not because of any cynical assumption that Muslim Americans are naturally traitorous and can't be trusted in the military, but because we've seen this before: in Yugoslavia.