Gaiden shares many similarities with its predecessor. For one, it takes place on a grid-based map, and each side will take turns moving their units across the map. When it's a player's turn, they'll be given the chance to move every single one of their units if they wish, though they're not required to. Once they move their unit in the attack range of an opposing force, they'll be given the chance to attack them. One of the unique aspects of the Fire Emblem series is that if a character dies, they are permanently dead, unable to be used again. In the previous game each weapon the player wielded had a set amount of uses before breaking, which is not the case in this game, though this would not be the case in future iterations of the series.This is the first game to have more than one main character promote, as well as the only of the entire series to let the player roam the towns freely and allow them to return to previous stages. Spells are learned throughout the game (instead of being items) and everytime they are used they drain a hit point from the user.
Rigel and Zofia, two countries in the continent of Valentia, are at war and two good friends Alm and Celica are thrown into the fray. Alm leads the Liberation Army against the corrupt Prime Minister of Zofia, and Emperor Rudolf of Rigel. Celica leads her own army to rescue the Earth Mother Mila, and stop the poisoning of the land by the God Duma. As the game progresses each main character learns more of who they actually are and what they are supposed to be.