After defending Fort Jinya from the Nohr, you reach the Wind Tribe Village in search of Ryoma and Takumi.
Before the Battle
Before you do the chapter 8 battle, you might want to do Paralogue 1: Tragic Start first. You will get a new unit by doing so, and you can bring that new unit to the chapter 8 battle to earn more EXP.
Rout the Enemy
In the southwest corner of this map, there will be allies Hinoka, Azama, and Setsuna. You should send Corrin to talk to Hinoka. After that, Hinoka and Azama and Setsuna will join you.
Setsuna starts at level 1, so be sure to have her fight some enemies to gain experience.
There are Dragon Veins throughout the map that will turn the sand into plains, allowing you to move farther per turn in those areas. You can ignore the Dragon Veins if you wish, to effectively slow down the pace of the battle.
The Archers' weapons are effective against flying units, so keep Subaki and Hinoka away from them.
Fuga has both an Iron Mace and an Iron Katana. He doesn't move from his tile, but he can attack 2 tiles away. He also starts using the Vantage skill when his HP are at 50%, giving him a chance to attack before your units strike.
After the Battle
You will be sent back to the castle with a new unit, Hayato. When you are ready, go to Chapter 9: Land of Gods.