The old Y/N died / A new Y/N rises

Y/N L/N was a normal student but he gets beaten from the other students in his school. He was blamed when something happened and the teachers didn't do anything to prevent this. Instead of helping the beaten student, they are having fun to see Y/N suffering. Someday, Y/N had it enough and left the school to search something better in his life. So Y/N decided that he would join the military. He was accepted and was immediately transferred to the Taskforce 141. What will happen if a war will start?