The Spearhead Squadron consists of those from the so-called "Eighty-six" who were exiled from the Republic of San Magnolia. They are fighting a tough battle against the Legion, autonomous unmanned drones of the Giad Empire. Although the squad has dwindled in numbers, the survivors are sent on a "Special Recon Mission"—a one-way trip to Legion territory with a 0% chance of survival.
Although it's a death sentence to which their homeland has condemned them, their leader Shinei Nouzen, along with Raiden Shuga, Theoto Rikka, Anju Emma and Kurena Kukumila, decides to go ahead and continue fighting.
They don't fight because they have hope or for the future. They keep fighting because the battlefield is the only place where they feel they belong.
[Source: Crunchyroll ES; translated]