Ranier was a pirate enclave which raided commerce around the Phoenix Wormhole Junction. In response, the Royal Manticoran Navy deployed heavy escorts to its commerce and fought numerous cruiser actions against Ranierian pirates between 1660 and 1662 PD. Its effort culminated in Commodore Edward Saganami's punitive expedition with five modern Manticoran battlecruisers against the Ranier System itself. He ended the war by terminating the Ranierian government.
After the pirates were defeated, there was a growing movement in the Manticoran Parliament to merge the Royal Manticoran Marine Corps into the Royal Manticoran Army for cost efficiency reasons. (Companion)
The Ranier War and the following anti-piracy campaign in the Silesian Confederacy convinced the Star Kingdom that it needed a more offensive military force, leading to the development of the Redoubtable-class battlecruiser. (JIR1)