The Resolve, a capital ship in the New Republic Fifth Fleet, has been classified in different ways, sometimes as a Star Destroyer and other times as a star cruiser.
Under the command of Commander Syub Snunb, the Resolve was part of the New Republic Fifth Battle Group. It had specially enhanced deflector shields with multiple layers, drawing power directly from the ship's engines. This design allowed the Resolve to withstand significant enemy fire, but it also meant that it couldn't simultaneously power its hyperdrive or other systems.
During Operation Hammerblow, the Resolve's role was to absorb the blasts from a hypervelocity gun located on Bessimir's alpha moon. This allowed K-wing bombers from the 24th Bombardment Squadron to attack the gun's emplacement. The hypervelocity gun's power was almost too much for the ship to bear, leading Commander Snunb to attempt an escape. However, the intense bombardment prevented the crew from lowering the shields and jumping to hyperspace. The gun ultimately destroyed the ship's outermost shield layer, the "D shield," along with its shield generator, before the K-wings successfully destroyed the emplacement.
In the novel Before the Storm, the Resolve is initially called a "New Republic Star Destroyer," which might suggest it's a Nebula-class Star Destroyer. However, it's later referred to as a "big cruiser," and the author's online FAQ clarifies that he envisioned it as a Majestic-class heavy cruiser.
The Complete Star Wars Encyclopedia also uses the term "New Republic Star Destroyer" for the Resolve without specifying a class. However, the entry for Syub Snub describes the ship as a "star cruiser," a term used in the sequel, Shield of Lies, to refer to the Majestic-class cruiser Indomitable.
As depicted in Before the Storm, the Resolve had to divert all engine power to its shields, preventing it from using its hyperdrive at the same time. The lack of any mention of the ship's own turbolasers suggests that the enhanced shield system also prevented the use of its heavy weapons. The novel doesn't explicitly state whether the Resolve carried starfighters, but its close cooperation with the BTL-S8 K-wing assault starfighters of the 24th Bombardment Squadron at Bessimir hints that the unit may have been stationed on board.