Here's a silly video of the laws received by Moses that Joshua would have been tasked with observing right after Moses.
Joshua is a part of the story that has been quite problematic. If we read it as genocide, then we endorse the Doctrine of Discovery, and the war, genocide, slavery and imperialism that Europeans have a long history of violently imposing on the rest of the world. I think it is quite valid to denounce such an understanding of Joshua. If it was genocide, then Joshua was flat out wrong!
However, another part of the context is what Jericho was (and represented), the powerful symbol of military might, military security, and economic oppression. Cities held the power over everyone outside of the city. Maybe Jericho is best envisioned by current day Manhattan and DC. How would you "fight" for your well being with those who control your life from skyscrapers, aircraft carriers and Kremlin-like fortresses? That is the question Joshua faced. It is far more likely Joshua was reminiscent of a Peasant Revolt rather than a powerful invading army. God was not with the powerful, but with those seeking life.
Still a problematic story, Joshua wrestles with how to engage the powerful in Canaan, and how to stay covenanted with a God that led them out of Egypt. I always wonder if they should have revolted in Egypt...
Today, as teenagers, how do we stand up to the peers and adults and systems in our life that can feel oppressive at time. Who do we stand up for, and is there a time when we are the ones in power, and need to react differently than Pharaoh and Jericho?