Lieutenant Carl Jaeger was a male Human Starfleet officer in the 23rd century. He served in the sciences division aboard the USS Enterprise in 2267 under the command of Captain James T. Kirk, during the historic five-year mission. He was one of the ship's meteorologists, and was fluent in the German language.
That same year, he was in a landing party that beamed to the surface of Gothos to search for the missing Captain Kirk and Helmsman Sulu. At the time the landing party was assembled, climactic conditions were thought to be extremely inhospitable, and his expertise in geophysics served the landing party well.
Trelane recognized Jaeger's name's national origin, gave a smart salute, and spoke to him in German, saying "Ein Deutsch Soldat, nein? Ein, zwei, drei, vier, gehen wir mit dem Schießgewehr!", while miming a military march. In response to Trelane's question ("A German soldier, no?"), Jaeger replied that his specialty was as a scientist, not as a military man. (TOS: "The Squire of Gothos")