The Mercury class battlestar was an advanced Colonial capital warship/carrier that served as the mainstay of the Colonial Fleet. They served as front ships of the line as well as as command ships. Having been first introduced roughly twenty years following the end of the Cylon War, and while still considered top-of-the-line vessels, the fleet was just beginning the process of phasing the oldest examples out of service, in favour of the newer Block II's and the Nova Class, at the time of the Fall of the Twelve Colonies.