Plot: Battlefield 2142: Northern Strike is an expansion pack for Battlefield 2142, taking place in Central and Northern Europe in 2145. It introduced new maps and vehicles as well as a new gamemode, Assault Lines.
Plot: Battlefield: 1942: The Road to Rome is an expansion pack for the Battlefield 1942 video game. It was released in February 2003 by Electronic Arts and developed by Digital Illusions CE. Wikipedia
Plot: Battlefield 2: Special Forces is the sole expansion pack for Battlefield 2. It is available either as a DVD, 2-CD retail package, or as a download via EA Downloader and Steam. It introduced new factions as well as new maps, vehicles, and weapons to the game.
Plot: Battlefield Play4Free was a first-person shooter video game developed by EA DICE and Easy Studios and published by Electronic Arts. Based on the Battlefield series, the game featured a modern warfare battlefield setting. Wikipedia