First lieutenant

First lieutenant is a military rank. A traditional infantry rank, first lieutenant is the second lowest officer grade, senior to a second lieutenant. Infantry lieutenants fall below captains, and command a platoon, consisting of about thirty troops. In comparison to naval ranking systems, a first lieutenant is equivalent to the grade of lieutenant junior grade.

This rank was used by the armed forces of the United States on old Earth, represented as a uniform insignia by a single silver rectangular bar. A US Marine 1st Lt. assigned to aircraft carrier USS Enterprise (CVN-65) was one of the troops involved in the hunt for intruding time traveller Pavel Chekov in 1986. (Star Trek IV: The Voyage Home)

The Marine 1st Lt. was played by Donald W. Zautcke, an actual USMC officer.

In the German armed forces of the World War II era, this rank was also used, translated as Oberleutnant. An Oberleutnant of the SS was called an Obersturmführer. The collar rank insignia for this rank was three pips in a diagonal line, with a single stripe beneath, on a square field bordered by white (a single pip was also worn on each epaulet). In an alternate timeline where Na'kuhl time-travellers had allied themselves with Adolf Hitler's Nazis in 1944, an Obersturmführer first lieutenant named Ghrath was executive officer to Vosk. (ENT: "Storm Front, Part I")

This chart shows only general equivalencies based on the ranks used by many governments on Earth, as well as the rest of the galaxy.