John G. Hemry is an American author of military science fiction who draws on his experience as a retired United States Navy officer. His background in the Navy has informed much of his fiction writing, lending authenticity to the military elements in his work. Hemry has written several series across different subgenres. Under his own name, he created the Stark's War and Paul Sinclair series. Writing under the pen name Jack Campbell, he has authored twenty-one volumes of The Lost Fleet series, which has become his most prominent work. He has also written The Pillars of Reality series, which blends steampunk and fantasy elements. Beyond his novels, Hemry has written over a dozen short stories, many of which have been published in Analog magazine. He has additionally produced a number of non-fiction works, further demonstrating the range of his writing career.