Interesting that the Navy has no equivalent to brigadier, and that a navy Captain has a much heft as a birgadier. However, I think that the significance is that the choice of those who get that second and that third star will be drawn from a different pool than before. I am sure there will be many O-6s who are disappointed who several years ago thought they were sure to get their stars. AND if Petraeus is successful in Iraq, he could become the next George Marshall and leave his stamp on the army long after his retirement.
I’m not an expert on the Navy rank structure, but I believe that an Rear Admiral (Lower Half) wears one star and is an O-7. The old O-7 rank of Commodore is obsolete, although I have read that the rank still exists and is used under certain circumstances.
In any event, Navy officers have far more “helf” than their Army counterparts. Commanders - 0-5, the equivlent of an Army Lt Colonel - exercise in their capacity as ship captains far more independence than battalions commanders exercise. Its inconceivable that any Army officer below the rank of Lt General would have the freedom possessed by captains of nuclear submarines or aircraft carriers.
This sort of authority breeds in naval officers a capacity for creativity and independent thought that few Army officers ever develop. Such differences are a shame, perhaps, but seem inescapable given the demands of the respective services.