Xanthus performed excellently at the Academy, despite his losses. Knight proved to have an excellent tactical aptitude, along with a genius-level intelligence. At the urging of a few professors, Knight also entered into a more Command-oriented program, where he also excelled. Late in his junior year, seeking to fill in some holes in his course schedule and hoping to improve his class standing, Xanthus also entered into a law/political program. Knight graduated at the top of his class, given the rank of lieutenant junior grade. Starfleet Intelligence enrolled him in further tactical training upon graduation, but only for the duration of a year, due to the urgency of the Cardassian/Federation War.
Knight was placed aboard the Ambassador-class USS Essex, which was on the front lines. Xanthus often went in with ground troops and distinguished himself numerous times in combat. An opening on the USS Golden Hind, a New Orleans-class vessel, was accompanied by a promotion to full lieutenant. During his assignment aboard the Hind, Knight was officially integrated into a Starfleet Intelligence team, under the command of the Captain of the Hind. Knight performed skillfully and after saving his team from a Cardassian trap, Knight was transferred to the position of Chief of Security and Tactical Operations aboard the USS Crockett, a refit-Excelsior working under the direct orders of the Starfleet Intelligence. The Crockett performed mostly snoop and run missions, but participated in two major Federation offensives. Knight recieved numerous commendations for his actions aboard the Crockett, resulting in his promotion to lieutenant commander and posting to the USS Maijus, a new Nebula-class starship in mid-2362. The war between the Federation and the Cardassians began to cool down around this time, and the Maijus primarily served as a stand-by vessel.
Knight took his first extended shore leave during this assignement, returning to his home on Tohvun III. Much of his world was in ruins, which greatly saddened him. During his shore leave, Knight renewed his relationship with an old girlfriend, Rebecca Phillips. The two were wed shortly before Xanthus' three month leave ended.
Upon his return, Knight was once again placed on the roster of a Starfleet Intelligence team. During much of his assignment onboard the Maijus, Xanthus was on missions with his Intelligence team, primarily targeting the Cardassians, Talarians, and Tzenkathi. It was during these missions that Knight was first declared one of Starfleet Intelligence's top operatives. He once again took extended shore leave after nearly two years, upon the birth of his son, Brian in 2364. Knight returned to the Maijus briefly before recieving a promotion and posting to the USS Sierra as first officer.
Knight obtained his first command of a Starfleet Intelligence team during this assignment, which rarely undertook any missions, as he spent those four years properly building his team. Xanthus recieved the praise of the Captain of the Sierra, and in 2368, Knight was promoted to Captain and given command the of the Nebula-class USS Monitor. Most of the senior staff aboard the Monitor was made up of Knight's Intelligence team. The ship eventually fell under the direct control of Starfleet Intelligence and served as a platform for Intelligence missions directed inside of the Federation. The Monitor earned a considerable reputation during its missions and Knight was considered one of the top captains within Starfleet. He was known to sympathetic to the Maquis resistance when it began in 2370, but refrained from joining. However, the loss of his wife and son in late 2371 to a Cardassian raid caused Knight to re-evaluate that choice. After much consideration on his part, he left Starfleet and started his own Maquis cell. With the extermination of the Maquis in late 2375, Knight, one of the few survivors, returned to the Federation. Due to the war with the Dominion, charges against Knight were dropped and he returned to active duty after a couple months' debriefing.
