Lieutenant-Commander (GA)
The rank of Lieutenant-Commander is a rank above Lieutenant and below Commander in the GA Military. The rank of Lieutenant is the third highest of the so-called "commanding officer ranks". The holders of this rank are usually in command of a larger entity of personnel serving under them than i.e. Lieutenants do. Lieutenant-Commanders can also serve as specialists of a certain field - such as medical personnel, and are a common sight in the bridge crews of a vessel, too.
The ground forces equivalent to a Lieutenant Commander is Major in the Gigerdian military ranking system - not Lieutenant Colonel. Lieutenant-Commanders often serve aboard starships in various bridge officer-roles, and quite often the chief engineer aboard a starship holds this rank.
Lieutenant-Commanders are also only suitable to act as 2nd or 3rd in command of a military vessel if they have completed a voluntary course for it. Lieutenant-Commanders are, however, qualified to act as commanders of smaller stations and outposts with their training - but not larger fleet support bases or somesuch.