Desert Warrior
Desert Warrior is a trait in Symphony of War that makes the squad immune to Heat Wave and Desert movement penalty. As such, it is useful on maps with a lot of desert tiles. It protects the squad against the significant morale losses sustained when in desert tiles during heat wave weather. It also provides a boost to movement through these tiles, making the squad more mobile on these chapters.
This trait has a very limited use, and mostly toward the end of the game. In total, there are only 3 chapters where this trait can be beneficial: Chapter 24, Chapter 25, Legends Chapter 6, and Gold Arenas.
If possible, it's recommended to change this trait to something else after you complete chapter 25 and Legends chapter 6, as it won't be useful anymore. Even if you're planning to use the unit again as squad leader for your next cycle in New Game+, it's still recommended to do so as this trait is only useful late in the next cycle.