Lieutenant

Lieutenant was a military or police force rank that represented an under-, or junior, officer of commission. This rank, and its derivatives, were often the second tier of commission in most militaries, and the third tier of responsibility in police forces.

Galactic Empire
The Galactic Empire utilized the lieutenant rank throughout its varied forces, including the Imperial Navy, Imperial Army, and Stormtrooper Corps. In the Army and Stormtrooper Corps, a lieutenant typically commanded a platoon. On a smaller to medium sized vessel in the Imperial Navy, a lieutenant may be a senior officer, possibly the vessel's executive officer. On a larger sized vessel, such as a Star Destroyer, a lieutenant was not high enough to command, but was usually in charge of a section of a vessel's operations. A lieutenant could also be an aid to a senior officer.

A lieutenant was usually still green (compared to field grade officers) but had more experience than a Sublieutenant and demonstrates further tactical thinking and leadership.

New Republic
In the New Republic, the rank of lieutenant was used by the Army, Starfleet, Starfighter Corps, and other services. In the Army, a lieutenant commanded a platoon. In the Starfleet, a lieutenant could be an executive officer on a smaller ship or oversee a section on a larger vessel. In the Starfighter Corps, a lieutenant was a senior pilot in a squadron.