always a navy medic that is transferred to the marines, etc and for all purposes from there on forward is part of the unit. My great uncle was attached to the 4th marine division during world war 2 in the pacific like this, spent his entire time with the marines with 90-95% causalities to the division (Siapan, Tinan, etc). When you die it still says Navy on the grave, even though the entire experience was with the Marines, sort of insulting.