Who is Mike Birkman from Johnny Got His Gun and what is their importance?

Mike Birkman is Kareen Birkman's father, a tough, excitable twenty-eight-year veteran of the Wyoming coal mines, now reduced to being a "railroad bull", Mike Birkman has learned to hate everyone: Wilson, Hughes, Roosevelt, socialists, and even Debs (a little). Nevertheless, he orders Kareen and Joe Bonham off the couch and into her bed on the eve of Bonham's shipping out to the Army and serves them breakfast in bed in the morning.