B'rel class
The B'rel-class bird of prey has been the premier multi-purpose warship of the Klingon Empire since its inception in the late 23rd century. Although over a century old design, the B'rel-class is only the latest in a long line of Bird-of-Prey designs within the Klingon Empire. Typically used as a scout, the B'rel-class is also used during times of war in packs, or wings, for attack runs against larger, sometimes stationary, targets. Although typically outgunned by cruiser-type vessels, the B'rel is small, agile, and highly maneuverable while still being able to inflict high amounts of damage. This gives them the ability to hold their own against many other ships that 'outclass' them and also makes them the perfect warship for Klingon attacks on enemy starbases and planetary outposts.
The B'rel was seemingly a test bed for many Klingon technology designs. The B'rel, like all Bird-of-Prey's, is capable of sustained atmospheric flight and planetary landing in an improved state from it's predecessors. The B'rel was also the first Klingon design to use the newly developed Klingon cloaking device, gained from the Romulans in the 2260s, in widespread application across the Klingon fleet. This also later led to the research and development of a B'rel-class that could fire it's on board weapons while cloaked; a feat that eventually proved worthless and faulty in nature and was abandoned shortly thereafter.
The B'rel-class was originally fielding in the early-2280s to replace the older Bird-of-Prey's that had been in service since the 2130s. The design was quite similar cosmetically, yet upgraded in nearly every way. When isolinear circuitry replaced duotronic computer systems throughout the Klingon Empire in the mid-2270s, the B'rel was given the newest systems and the potential upgrade capabilities that were far superior to that of it's previous counterpart. The first B'rel encountered by the United Federation of Planets was during the Genesis Incident and indirectly caused the destruction of the USS Enterprise before it's commander and crew were killed and the B'rel captured by Captain James T. Kirk.
From there the run-ins with the B'rel on the frontier against both the Federation and Romulan Star Empire increased exponentially. This was primarily due to the ability to quickly build the B'rel-class and rush them to the front lines. Well into the 24th century the B'rel continued to get massive upgrades after upgrades due to it's versatility and the original designers giving the B'rel massive upgrade abilities.
However, although the B'rel had been in service for nearly a century, it received it's largest litmus test during the Dominion War in the 2370s. As the Klingons entered the war against the Dominion they largely found themselves resposible for counteracting the Dominion's main arsenal: the Dominion attack ship. Originally the Dominion attack ships quickly overwhelmed the Klingon B'rel-classes showing clearly superior weaponry and tactics. However within only a few weeks the Klingons were able to develop new techniques for fighting enemies that were so unlike anything they had encountered before. Using Federation shield upgrades on their own ships, and a few tweaks to their weapons systems, the B'rel proved to be the match for the Dominion attack ship that they had never encountered before. Nearly toe to toe in every way, the remainder of the Dominion War was riddled with pure tactics and ship commander experience when the two ships every came head to head.
The B'rel proved to be very successful against the Dominion attack ships; so much so that the Klingon flagship, the Rotarran, was a B'rel-class Bird-of-Prey. After the conclusion of the war the Klingon Empire upgraded some of the internals of the design once more, planning to continue it's use even after a century, and began massive ship building operations of the B'rel to recooperate their massive military losses during the war. While the B'rel is over a century old design it continues to prove to be useful, versatile and upgradable. Plans have begun for a new generation of Bird-of-Prey, but with the massive numbers of B'rel-classes out in the Klingon fleet, and their continued production, it is unlikely they will be going out of favor with Klingon captains in the near future.