Defend or Rescue are map objectives used throughout the Fire Emblem series
Defend and Rescue are similar in nature as both require the player to complete a map by preventing an enemy unit from reaching a certain tile.
In Defend maps, players must prevent the enemy from reaching a specific tile on the map, usually one that is positioned behind the player's starting position or at a far side Village. If an enemy unit ends their turn on that tile or next to the village, a Game Over immediately triggers. To clear the map, players must either Survive a certain number of turns before the enemy is force to retreat or must rout all enemies that appear.
Rescue requires that the player kill specific units on a map before they reach a certain tile which is usually a distance away from both the enemy and allies. Maps that feature this objective usually revolve around an character being kidnapped. If the objective is solely Rescue, only the highlighted unit must be defeated. Occasionally, this is paired with Rout the Enemy as well.