As the Rebel Alliance began to acquire Galactic Republic-era Rendili StarDrive Dreadnaught-class starships, it found the required 16,000-being crew to be difficult to manage and procure, yet they were in desperate need of warships.
After equipping Dreadnaughts with droids and automated systems to reduce the crew requirement to 5,000 beings, thus rendering the ships usable, Rebel engineers began modifying Dreadnaughts to allow for greater speed and efficiency while retaining the original weapon systems. The final product was only recognizable as a descendant of the Dreadnaught-class by the nose of the ship. Most of the internal structure was exposed to space, while a dorsal and ventral fin provided added maneuverability.
These modifications removed the internal docking capacity of the Dreadnaught-class, but the ships were equipped with 20 umbilical docking fixtures like those on the EF76 Nebulon-B escort frigate. Unlike the Nebulon escort frigate however, these docking fixtures could not carry other ships through hyperspace. In addition, the assault frigate carried a modified assault shuttle on its back, which was secured in a manner that allowed it to be carried in hyperspace.
The assault frigate had a larger number of weapon emplacements than the original Dreadnaught, but the turbolasers had a shorter range and slower fire rate due to the increased demand on the main power system. The removal of large quantities of hull plating reduced the ship's durability, but slightly stronger shields partially compensated for this.
The Assault Frigates generally had one prong at the bow, but variants were equipped with split-bows.
A twin-pronged variant fought in the Assault on Kamino in 1 BBY The ship reverted from hyperspace along with the rest of the Alliance Fleet ships to face three Imperial Destroyers.
Assault frigates first also combat around the time of the Assault on Kashyyyk of the Galactic Civil War. They served as a mainstay of the New Republic Defense Fleet in the years following the Battle of Endor.
The frigate was tweaked into the Assault Frigate Mark II, and although the Mk. I remained in operation, the Mk.II production line failed.
The refits were expensive and time-consuming, but the Assault Frigate was considered to be a very effective combat warship. Though these warships were unique to the Rebellion/New Republic, the Empire made efforts to acquire them—a rather ironic reversal of fortune.
The name of this ship class is a proper noun as well as a description of the vessel type. To aid in the potential confusion, the ship was commonly referred to as the New Republic assault frigates or Rebel assault frigates by Imperial forces.
One Mark I frigate was used to make up a secret retreat in 137 ABY.