As a close friend of Senior Chief Petty Officer Miles O'Brien, Dr. Bruce Burke was a veteran instructor at Starfleet academy before being assigned to the Republic as Chief Engineering Officer during the Tholian encounter at Sigma Omicron V. He is credited to have uncovered and dealt with an infestation of interphased parasites he identified as "Subspace Termites" that infected the engineering subsystems of the ship. Burke is also credited for diagnosing the faulty reactor towers of the terraforming operation at Sigma Omicron, reinforcing the station's shields when the planet's crust turned to an ocean of lava, and rescuing the away team from the surface. After contracting a rather severe form of Streptococcus astris while at Sigma Omicron, Burke required lengthy recovery and convalescence after the mission, necessitating his reassignment back to Earth.

Lieutenant Danzig reported aboard the Republic as Chief Tactical Officer while docked at Starbase 39 Sierra shortly before a mission to the Sigma Omicron system. He had little time to adjust to his new position before Republic found herself in battle against a fleet of Tholian vessels. After the Republic was ensnared in a constricting energy web, and the hull began to buckle under compression stress, Danzig was killed while evacuating forward sections of the ship. The lieutenant sacrificed his life to rescue several dozen personnel by sealing a bulkhead from the outside against decompression. Due to his selfless action, Lieutenant Danzig was posthumously awarded the Christopher Pike Medal of Valor. He is survived by his wife Alice.

Hranok's previous assignment indicated he took his job seriously while on duty, but was also an open-minded, curious and friendly person. He often worked as a bartender while off-duty and enjoyed socialising with his crewmates. After Hranok reported aboard Republic at Starbase 39 Sierra, he took up the duties of Chief Science Officer, and accompanied the away team on the mission to Sigma Omicron V. During that mission, it turned out that the Bolian was actually an impostor named Evok, who was sent by the Orion syndicate to kill a member of the Republic senior staff. As it turns out, Hranok was an assumed identity expertly planted in the Starfleet personnel database, and Evok was taken into custody. He committed suicide before he could be put on trial for impersonating a Starfleet Officer and conspiracy to commit murder.

Naruko Kuga was a young Starfleet Ensign fresh out of the academy when she reported onboard the Republic as Chief of Operations. In both the academy and elsewhere, Kuga was known for getting into trouble, but usually as a victim of circumstance rather than a perpetrator. While Kuga's personnel file indicated she was a human female who led an ordinary upbringing on Earth, it turns out that her origins were far more sinister. With only days into her tour on the Republic, Kuga was kidnapped and reunited with her true past in the Gamma Quadrant. Unbeknownst Kuga, it turns out she was an organically-grown, biomechanical organism with the power to manipulate complex computerized mechanisms. Conceived by a rouge admiral operating out of a secret base, Kuga was designed to interface with a highly-advanced, powerful spacecraft with orders to start another war with the Dominion Founders. Escaping her captors before carrying out the fiendish plot, Kuga found herself back aboard Republic where she placed in protective custody. With the aid of yet another Starfleet impostor, Kuga beamed off the Republic to a nearby cloaked vessel which was accidentally destroyed in a transwarp-tractor beam mishap.

James Marshall prided himself on being a direct descendent of a United States president from Earth's pre-unification political history. At Starfleet academy, he was known on campus for being a "hot-shot" and "very cocky". After graduation, he was assigned to the USS Archer and eventually promoted to full lieutenant before being transferred to the USS Gettysburg where his captain highly reccommended that he attend Starfleet Command School. After completion of command school, Marshall was assigned to the USS Chekov as where he was promoted to Lieutenant Commander and made Second Officer of that vessel. Following that assignment, he was promoted to Commander and assigned to the USS Eagle as Executive Officer, and remained in that position for a year before being offered command of the Galaxy-class USS Republic. A few months later, Marshall was killed during the Cestus III incident of stardate 57502 after challenging a Gorn starship officer to personal combat.

Assigned as Chief Tactical Officer of the Republic while docked at Starbase 23, McClintock was noted as being very confident in his abilities, despite a tendency to second guess himself constantly. He had a very short, very violent temper, and displayed a tendency to shoot first, and use deadly force in self defense and in the defense of others when lesser force would have been sufficient. During the Cestus III incident of stardate 57502, the captain of the Republic was killed, and McClintock, together with the assistance of the chief science officer, was forced to take command of the Republic due to classified orders from Starfleet Command. The other senior officers of the vessel were unaware of these orders, and assumed that McClintock was attempting to mutiny. After the resolution of the incident, which included rendering McClintock unconscious, the lieutenant was exonerated by Starfleet Command and reassigned.

Kristen Tyler was assigned to Republic after serving as Assistant Science Officer aboard the USS Harrison, where she was noted as being easy going and a hardworker, expecting the same from those under her command. She had little tolerance for crewmen who didn't live up to their responsibilities. Upon reporting aboard Republic at a stopover on Starbase 23, Tyler took up responsibilities as Chief Science Officer. She was credited to have analyzed the hull structure and integrity of Gorn warships during the Cestus III incident of stardate 57502. During that incident, Lieutenant Tyler was forced to act upon classified orders and assist the Chief Tactical Officer in assuming command of Republic after the captain was killed. Unaware of the clandestine orders, the other senior officers of Republic mistook her actions as an attempt at mutiny. After the resolution of the incident, Lieutenant Tyler was exonerated by Starfleet Command and reassigned.