Complex sentence: The last submarine commissioned for the "41 for Freedom" submarines was the USS "Will Rogers" (SSBN-659) which was formally decommissioned and stricken from the Naval Vessel Register on 12 April 1993, but she was not the last FBM submarine decommissioned.
Split into simpler sentences: The last submarine commissioned for the "41 for Freedom" submarines was the USS "Will Rogers" (SSBN-659) which was formally decommissioned and stricken from the Naval Vessel Register on 12 April 1993. Though she was the last built, "Will Rogers" was not the last FBM submarine decommissioned.