John G. Hertzler was born in Port Royal, Pennsylvania, USA. His father served in the U.S. Air Force, so the family had to move many times.
Among other places, Hertzler lived in many different places in the US, like Texas, Casablanca, Omaha and Maryland.
John was very successful as a football player for a couple of years after High School, he even played for Bucknell University, before he devoted himself to theatre.
He played the Klingon General “Martok” in several Star Trek: Deep Space Nine episodes as well as two other roles - A Vulcan captain and a character named “Roy Rittenhouse”. In Star Trek Voyager he embodied a Hirogen hunter, who had to fight Seven of Nine in a kind of wrestling arena in the episode called „Tsunkatse“
In addition, he had guest roles in Six Feet Under and many more TV series like Roswell, or Sabrina, the Teenage Witch.
Besides acting he also worked for a theatre company. In 2009, Hertzler directed an outdoor production of A Midsummer Night's Dream for the Ithaca Shakespeare Company.
In November 2013, Hertzler was elected as a Democratic candidate for a two-year term on the town council of Ulysses, New York. He is currently serving a term that will end in 2020.