ISS Yorktown

In the mirror universe, the ISS Yorktown was an Imperial Starfleet vessel in service in the 23rd century. 
In 2277, the Yorktown was one of several vessels that were assigned to Grand Admiral Matthew Decker's task force, for a plan to ambush and destroy the ISS Enterprise in the Terra Nova system. 
When Admiral Spock executed his takeover of Starfleet, the commanding officer of the Yorktown indicated that he was neutral, and followed the rest of the fleet when they were assigned to patrol the Klingon border.