Battle of Talania
From FreeSpace Wiki
The Battle of Talania was one of the turning points of the Terran-Vasudan War. After the Battle of Gulnara, it appeared as if the Terrans would win the war, and production of the GTC Leviathan-class of cruiser was halted. However, the GTA later suffered a significant defeat in the Talania system which caused production to be restarted.
Nothing is known of this event beyond what is stated in the FS1 tech entry for the Leviathan. There is no additional info so it is impossible to quantify the number of GTA and PVN forces involved.