Replying...
Intro. On the planet he had problems with war and with nature, with human beings. Now countries make a group of teenagers and adults, so that they can fight (you can put who they fight with) Now these countries teach everyone to speak other languages, since they must communicate. among them. So ah happened. In a research group he makes large teams since each military officer is going to put a team between them. (They will have other uniforms or decide which uniform to wear.)

An apocalyptic world (City, countries in ruins)

@ARLETTE