Developed during the same time period as the Excelsior Heavy Cruiser, the Defender project was tied closely to other projects that were studying the ramifications of esoteric warp nacelle configurations. Like the Constellation Patrol Cruiser, the Defender Fast Cruiser was to use two pairs of warp nacelles to allow it to achieve higher warp field efficiency. The need also existed for a new generation of main line cruiser hulls to replace the aging Constitution and many new projects, including the Defender, were top contenders for the role.
The Defender project was progressing nicely with half a dozen hulls completed by 2285. Despite the advances made in the Defender and the relative success of the models currently on their shakedown cruisers, the Excelsior proved in all ways superior. Not only did the ship sport a sturdier frame, more advanced sensors, and more firepower, it also proved to be a more flexible ship.
Construction of new Defenders ended overnight. The last ships were kept in service, most being placed into the defensive fleets of the Federation core worlds. When the Borg attacked the Federation in 2367, several of the last Defenders joined the fleet that was massacred at Wolf 359. The last Defenders saw service during the Dominion War defending the homeworlds again, and the last two Defenders to survive that conflict were finally retired from service, the ships scuttled.