 Series creator J. Michael Straczynski (qv) once said that the  Earth Alliance military used a "blending" of rank systems, although  this was never spelled out in detail on the show. Thus, the exact EA  rank structure remains unknown, although most fans assume the  different branches (Navy, Marines, Security) each use the  appropriate system of ranks for that branch. (Contrary to popular  belief, Admirals have been mentioned twice on the show, in "And the  Sky full of Stars" and "Signs and Portents") There are Generals who  have been seen wearing the blue Navy uniform, although this could be  evidence of yet another branch (Air Force?).