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

Howie is Joe Bonham's childhood acquaintance, not quite friend, with whom he goes to the Uintah desert to lay track after Howie loses his girlfriend, Onie, and Bonham his girlfriend, Diane, to rich Glen Hogan. The impetuous adventure overwhelms them physically, and when Howie gets a telegram from Onie asking to be forgiven, they catch a coal train home.