The threat of a starship being boarded and captured by enemy forces appears often in Star Trek franchise. On some occasions, such an operation is successful and the enemy gains the control over the starship. Such a starship is of great value for the enemy's intelligence services and would most likely be disassembled and studied by them. However, in situations when the ship's design is already known, or several ships of the same class are captured, there is no need to disassemble every one of them. Such ships can be manned by the enemy and be incorporated in the enemy's fleet.
There have been episodes in which a captured enemy ship is used for covert operations, however these ships do not last for long (like the Dominion's ship used by Starfleet).
Conditions I would like to exclude:
- A captured ship used by an individual and not in actual control of enemy's fleet (like Dukat's Bird-of-Prey).
- A captured ship used in one major operation and not used continuously by the enemy due to its destruction / becoming disabled / not being shown ever again (like Jem'Hadar fighter captured by Starfleet).
Have we ever seen a captured ship incorporated permanently in the enemy's fleet?