They were always a separate branch, but anytime you are on board a ship you technically fall under the command of the ship's captain (this is true of anyone, not just Marines) and back then Marines spent even more time on board ships than they do now. It's probably correct to say that during that time they were more subordinate to the Navy because they were basically dependent on them for transportation.Jones,
We are talking about their relationship in the first decade of the nineteenth century during The Barbary Wars. i.e. - shores of Tripoli
I thought the Marines started out under the command of the Navy.
Can you shed any knowledge during that period?