Jack Campbell is the pen name of John G. Hemry, an American author known for his military science fiction novels. Drawing on his experience as a retired U.S. Navy officer, Hemry writes stories that blend tactical realism with engaging narratives. His most famous work is The Lost Fleet series, which follows Captain John “Black Jack” Geary as he leads a fleet through enemy territory during an interstellar war. The series is praised for its strategic depth and character development.

Campbell has also written spin-offs like The Lost Stars and Beyond the Frontier, as well as the prequel trilogy The Genesis Fleet. His other works include the Stark’s War and JAG in Space series, which explore military themes in futuristic settings.