Thomas Graham was a Major in the United States Marine Corps who, after serving in Operation Just Cause and as a member of Forces Reconnaissance, became leader of SG-14. In 2000, he was captured by the Goa'uld on a mission to P6Y-325 and brainwashed to assassinate Per'sus, the Supreme High Councilor of the Tok'ra. After failing to kill his target, he took his own life.
Born on August 27, 1968 in Brewer, Ohio, in the United States of America, little is known of Graham's life before he joined the Marine Corps at the age of 18. Recruited into the Marine Corps Recruit Depot Parris Island, South Carolina, he received the standard technical training with the Colt M16A3 rifle and M9 pistol and was one of the first to use the M249 Squad Automatic Weapon when it was released in 1987. Graham saw his first military action in 1989 during Operation Just Cause in Panama where he was distinguished for his bravery and given the Armed Forces Expeditionary Medal.
Within a year of this, Graham had managed to pass rigorous tests and requirements in order to join the Forces Reconnaissance, an elite group within the already elite Marines. As such, Graham became part of a six man team which was trained to drop behind enemy lines under the cover of darkness in order to seek out enemy positions and report the locations of any such encampments to their Commanders. In addition to this, the team was also required to know how to find cover in even the most desolate environment in case they were ever discovered by enemy troops. (SG1: "The DVD Collection 17")
Some time before Stargate Command's fourth year of operation, Graham was recruited to serve as the Commander of SG-14. One of the missions this team was involved in was to the planet P6Y-325 where they made contact with the local primitives known as the Lasarians. While there, however, Graham and his team were captured by an unknown Goa'uld who brainwashed both Graham and Lt. Louise Astor into becoming Za'tarcs in order to get them to kill the Tok'ra Supreme High Councilor, Per'sus. As such, Graham and Astor were given memories of fleeing from Horus Guards and making it to the Stargate; whether or not this happened remains unknown, as it is unclear which memories are real and which are false when Za'tarc brainwashing was involved.
Graham continued his normal duties, and was sent with SG-14 to support Earth during the negotiations between the Tau'ri and Tok'ra. While on Vorash with SG-1, the Tau'ri were introduced to Per'sus and immediately Graham's Zatarc brainwashing took over. Quickly constructing a weapon of unknown Goa'uld design, Graham fired on Per'sus but was unable to kill him as another Tok'ra jumped in the line of fire. Though Graham was obviously in pain and was trying to fight off the brainwashing, he was unable to do so. Again his Za'tarc brainwashing took over, deciding that he was unable to take out his target, and Graham activated the second function on his weapon which caused it to explode and kill him. (SG1: "Divide and Conquer")