USS Union, NCC-93218-D The fourth USS Union was a Starfleet assault cruiser assigned to the Alpha Centauri Institute under the command of Captain Shandra Jerro until its destruction in 2405.

The Union was on patrol in the B' Tran Cluster when it picked up a Distress Call from the research vessel USS Orinoco and set course toward her at maximum warp. The Union arrived in the system and located the Orinoco but detected no lifesigns aboard. Readings indicated that life supports was still functional, and an away team was sent to find out what happened. However, before the team could board the disabled ship, itswarp core breached without warning and knocked out the port shields and primary communications array of the Union.

As Captain Jerro attempted to maneouver in preparations for warp, further damage to some of the ship's maneouvering thrusters was discovered. While in this vulnerable state a Borg sphere came from the otherside of the nearby planetand fired a full spread of plasma torpedoes all of which hit the now unshielded port side. After a brief engagement, the sphere disengaged and warped out, only to be replaced shortly after by another Borg sphere with a third, larger Borg vessel detected on sensors and identified as a Borg Tactical Cube.

Already suffering from a lack of shields, multiple hull, breaches, and low power-levels to weapons, the Union attempted an emegency warp out, but could only achieve Warp 4, not enough to outrun its Borg pursuers. Another skrimish followed, with the Union taking refuge in a nearby nebula until repairs were completed on the communications array. Evading the Borg, the Union managed to return to the Sirius Sector Block were it was met by the USS Rainier and USS Masamune. Those vessels were able to evacuate the remaining crew shortly before the Union was destroyed as the result of Borg nanites that had been transferred to the ship's main systems during the battle.

Captain Jerro later faced Court Martial over the loss of the Union but a panel that included Admiral Quinn and ACI Vice President Cara McFerran cleared her of any blame in the incident.