Protect is a map objective used throughout the Fire Emblem series
Protect requires that the player prevent an enemy from killing specific Ally Units. Ally units are typically very frail with weak stats, do not attack, and may die from a singular hit. The player must defend set character(s) or else a Game Over is triggered. Some Protect maps require the defense of a single Ally Unit while some require the defense of multiple.
Protect is sometimes used as an optional objective used on top of certain other objectives. These usually involve the player having to defend one or more Ally Units on the field. If multiple are deployed, the player is often rewarded with useful items and weapons based on how many Ally Units survived the battle.
If Protect is the primary objective, it has a additional requirement based on Survive objectives of defending the Ally Unit for a set number of turns or a Rout the Enemy/Defeat the Boss objective of killing all enemies on field or killing the Boss respectively.