Brinker's father is a representative of the older generation, the children of World War I. He wants his son to race bravely into the thick of the fighting, rather than to hold back and stay on the edges of the action. He encourages Gene and Brinker to become "heroic," or to take military jobs that would bring more respect. He says to them, "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" (p. 199). He wants the boys to be proud of the fighting they have done, and not to just run and hide from the dangers of war.
Gene and Brinker, however, see him as a part of the generation that has created the war. They resent him for sending them off to fight while he stays safely at home.