The Calgary class heavy troop transport was a type of starship that was prototyped in the late 23rd century. (Star Fleet Data File, vol. 1) The prototype was developed as a response to the phasing out of Federation-class dreadnoughts in favor of smaller and less costly Avenger-class heavy frigates as well as Starfleet Intelligence reports of increased production of the K't'inga-class (D7M) battlecruiser in the Klingon Empire. It was felt that a large, fast vessel was needed for the mass transport of personnel into a battle zone.