The Battle of Sector 2148 was one of the most intense and hard fought surface-to-space battles of the Earth-Romulan War, which involved Earth Starfleet forces against the Romulan Navy in the skies, and Earth's MACO forces opposing Romulan ground troops across six different worlds. It's size and dual-level of involvement is second only to the fight that ended the war, the Battle of Cheron. (Star Trek: Poseidon - The Birth of the Federation)