As Fallout is at pains to keep mentioning, war never changes. The fourth episode of Fallout season 2 makes that abundantly clear with a surprise pre-Great War flashback that takes viewers back to a conflict that was last seen in a divisive DLC pack from Fallout 3. Spoilers ahead!
While the title card in the new episode only says Cooper Howard is fighting his way through the 'Alaskan Front' in faulty T-45 Power Armor, it appears he's specifically in Anchorage as part of the Sino-American War (which, itself, is a slice of alternate history that's referenced in various pickups and background items in the game series).
