The SolarGuard of the 02260s and 02270s

Even as the VanGuard reached further out into the Great Deep to claim worlds for Terran humanity, the once-proud Solar Navy transitioned into a new force for the protection of the Sol System.  The SolarGuard, as it came to be called, served as an adjunct to the HomeGuard (itself composed of "down-commissioned" warships of the former UECON forces) with the assigned duty of protecting Earth, the Solar System and the colonies of the nearest systems.  The SolarGuard fleet used a standardized fleet of Defense Frigates, termed the Valkyrie class, as well as a limited number of larger warships, although in many ways these massive vessels duplicated the capabilities of the existing HomeGuard superdreadnoughts and thus were removed from the line of duty long before becoming obsolete. (The Valkyrie class also made something of a name for itself in exploring previously ignored systems of the known worlds while the Venture class did the same out on the Frontier). 

Valkyrie class Defense Frigates served side-by-side with their Venture class Light Exploration Cruiser brethren throughout the 02260s and 02270s, and some sixteen units remained in service into the 02290s to be upgraded/re-categorized from frigates to perimeter patrol cruisers.

The SolarGuard Valkyrie class Defense Frigates were designed with a mix of captured Qajari/Laythian technologies and Promedian building methods resulting in extremely capable, but costly vessels for their intended purposes. 

The Heaven's Will/Kusanagi class superdreadnought came into being when the Promedians offered technology enhancements to the Terrans as part of the foundational agreements that created the InterStellar Federacy.  In addition, advances made by reverse-engineering Qajari and Laythian technologies recovered from the prior conflict ensured these huge vessels were amongst the most capable warships fielded in the octant during their service life despite their limitations (such as not being very maneuverable in battle and requiring frequent and major maintenance cycles to remain combat-worthy).  Their tremendous cost made them easy targets for decommissioning as the VanGuard began to grow into the role of a single-fleet navy for the fledgling alliance.