The Tholian War was a series of conflicts that erupted between the United Federation of Planets and the Tholian Assembly from 2353 to 2360.
During this war, the Tholians demonstrated an uncanny ability to absorb punishment while striking vulnerable Federation rear positions along with using the dangerous areas of chaotic space to their advantage. It was noted that no core Tholian colony was ever occupied and Starfleet was only able to penetrate a few parsecs into the Tholian territorial annexes. The conflict ended when the Tholians requested a truce, something that caught the Federation by surprise. (Decipher RPG module: Aliens)