May I suggest that a military background would be a positive disadvantage to being SoS? The individual would have experienced only one part of the entire military family and could therefore, perhaps, favour one facet of the military over another simply because of their background and not on the facts presented at the time. One only has to read PPrunE to see the differing opinions expressed on a topic - often based upon the branch that the contributor had served in. (I would hate to use the ex-MPA chaps as an example here, but you see what I mean). Yes, military experience for one in Government is no bad thing but the SoS for Defence has to have an open mind and a blank canvas.