He is a final reminder of the war, and a way to bring the war front and central, once again, making it more of a real part of their lives. Things are changing, and Brinker's dad serves as the embodiment of embracing that change, whole-heartedly. There is incredible pressure from Brinker's dad to to join the war, to be part of the effort, to have glory and honor in it. He says,
"Your war memories will be with you forever...people will get their respect for you from that."
Not only should you join up, but you should join up where the action is most intense:
"if you can say that you were up front where there was some real shooting going on, then that will mean a whole lot to you in years to come."
So not only is advocating the war, putting pressure on them to join, he wants them not to play it safe, but to go to the most dangerous fronts so that they have bragging rights later on, so that they will be more respected. War is everything, unless they maintain a peace separate from that war, something that Gene says Finny was able to do. Before this chapter, war was hovering on the fringes of their lives; with Finny gone, war comes to campus completely and takes over, and Brinker's dad serves to show that more thoroughly.