The design of the Ambassador class, which entered service in 2322, was closely related to the Constitution class and formed the basis for the design of later vessels like the Nebula and Galaxy classes. Designed for long range exploration and defense of the Federation, the Ambassador class heavy cruisers served as Starfleet's the primary capital ships from 2322 through 2360, and were responsible for a number of first contacts, including that of the Zakdorn, who would go on to become Federation members, during the coreward frontier survey in the mid-24th century, and the class took the brunt of the fighting during wars with the Cardassian Union and Tholian Assembly of the 2340s and 2350s.
In the early 24th century, Starfleet Command desired a new class that could explore further beyond the borders of the Federation, and with greater safety, than before, and it was no accident that the Ambassador class mimicked the Constitution class, which was arguably the most successful starship design in Federation history, in appearance, if not in function.
Part of the Ambassador's rugged durability stemmed from its redundant and shielded systems. Electroplasma System (EPS) taps throughout the ships were the first to employ triple-redundancy, allowing the ships to continue to operate even after multiple hull breaches. The Type IX Phaser arrays employed on the class, new when the class was initially designed, had an efficient power use curve that allowed the ships to mount more arrays than prior designs. Many aspects of the design were beyond the capabilities and standards of the era, however, and in the end several key systems, notably warp drive, paid the price. The end result was a multi-role starship capable of operating independently on extended-duration missions, but one that was never quick to the scene. The Ambassador class was nevertheless a very maneuverable ship that could outperform equivalently sized Romulan vessels, and at the height of Romulan aggression against the Klingon Empire, Ambassador clas ships sometimes found themselves in—and holding their own against—three-to-one odds. These heroic displays, particularly that of the U.S.S. Enterprise NCC-1701-C in 2344, eventually paved the way to a formal alliance between the Klingons and the Federation.
Ambassador class heavy cruisers continued to serve with distinction in significant fleet actions and frontier patrol capacities for many years after production on the class ended in 2372. While outgunned by Jem'Hadar warships during the Dominion War, the Ambassador class still managed to wreak a deadly toll on the Cardassian Galor class vessels. Those Ambassador class vessels still in active service by 2375 continued to fulfill either patrol or training duties, as well as the occasional survey or diplomatic profile mission.