Post-Captain

In Britain's Royal Navy, Post-Captain is the rank acchieved after being Commander (from 1794; before that it was possible to become post as a Lieutenant and commander was an informal rank). An officer would become first a Junior Post-Captain and after 3 years become a Senior Post-Captain.

Once an officer has reached the rank of Post, nothing but death or a court martial can stop him from reaching the rank of admiral, or so thought the fictional character Horatio Hornblower (by C. S. Forester).

It is important to distinguish between Captains and Post-Captains. While an officer (not of the rank Post-Captain) commanding a ship is addressed as Captain (title) only on merits that he commands a ship, or rather a Sloop he has not reached the rank of Post-Captain. A Post-Captain is addressed as Captain (rank & title) and even if he is uncommissioned (does not command a ship) he is still addressed as Captain (rank).

A officer took 'Post' when he was first commissioned to command a 'post ship', a ship too important to be commanded by a mere commander.

A junior Post usually will be commissioned a frigate or a comparable ship to command, while a Senior Post will be commissioned a Ship of the Line.