A Republic marine was a member of a fighting force of the Galactic Republic. Imperial Grand Admiral Josef Grunger had been a Republic marine prior to the Republic becoming the Galactic Empire.
The Star Wars Insider article "Who's Who: Imperial Grand Admirals" was originally intended for Star Wars Gamer magazine prior to its cancellation, under the title "Dirty Dozen: The Imperial Grand Admirals." When the article was reused in Star Wars Insider, several details were omitted, including mention of Grunger as an "ex-Republic marine."
The Star Wars Insider article "Who's Who: Imperial Grand Admirals" was originally intended for Star Wars Gamer magazine prior to its cancellation, under the title "Dirty Dozen: The Imperial Grand Admirals." When the article was reused in Star Wars Insider, several details were omitted, including mention of Grunger as an "ex-Republic marine."