Commander ranks grew from ships too small for post captains

When did ranks between lieutenant and captain emerge in the Royal Navy?

Commander grew from the need to entrust a ship to an officer without making him a post captain, while lieutenant commander appeared later as nineteenth-century ships and officer structures expanded.

In the Age of Sail, some vessels needed an independent commanding officer but did not justify a post captain. The title master and commander described that assignment and evolved into the commander rank. As nineteenth-century ships and establishments grew, another grade between lieutenant and commander became useful. Lieutenant commander formalized that intermediate responsibility within a larger professional officer structure.