Defiant class

Starfleet began developing the Defiant-class starship as a means of defense against the Borg in the wake of the massacre at Wolf 359 and near-assimilation of Earth in 2367. Starfleet abandoned the project due to design flaws, and the seemingly-decreased Borg threat.

However, when the Federation learned of the threat posed by the Dominion in 2370, the prototype USS Defiant (NX-74205) was relaunched and assigned to station Deep Space 9, under the command of Benjamin Sisko. 

When the Defiant proved her value in combat against the Dominion, Starfleet commissioned other vessels of the class, many of which played decisive parts in the Dominion War and later conflicts with the Borg. (, et. al; )