The Expeditionary Forces is an was an Alliance of Lordaeron military venture during the Third War and their mission was to go to Northrend in order to hunt down and kill Mal'Ganis. It was led by Arthas Menethil. It was formed by Arthas right after the Battle of Stratholme. One month after the events of Divergent Courses, Arthas and Captains , , and landed on the coast of Daggercap Bay, Howling Fjord, Northrend. It was there that they established their base camp. Later, they discovered the Dwarven Expediton, lead by , and united to defeat the Mal'Ganis' Undead Pillagers.
Early the next morning, an Alliance Emissary shows up to the base and speaks with Captain Luc Valonforth. He tells them that Uther the Lightbringer had convinced King Terenas Menethil II to order the expedition to an end and recall it back to Lordaeron. Arthas, not wanting to end the hunt for Mal'Ganis, destroyed the Lordaeron Navy, with the help of ice troll, ogre, and goblin mercenaries. After his soldiers found the burned ships, Arthas blamed the mercenaries for it and they killed them.
The next day, the Battle of Drak'Tharon Keep happened. Arthas obtained Frostmourne and knocked out Muradin Bronzebeard, and defeats Mal'Ganis. Later, Prince and Captains and , along with transformed into the undead and return to the Capital City.