How does the allusion of blitzkrieg have an effect on the story/chapter?Some insights with the character of Finny would be helpful too.
Blitzkrieg is a term for a style of warfare invented by the Germans. It involves an all-out assault on the enemy. Finny's idea of "blitzkrieg ball" involves an all-out assault on anyone Finny decides needs to be attacked. The invention of "blitzkrieg ball" situates the boys' games in the larger context of WWII. Although at first the boys' lives are not directly affected, the war stands as an ever-threatening shadow, coloring their time and experiences at Devon. Finny of course seeks to emulate the soldiers, & his creation of "blitzkrieg ball" reflects that desire. The fact that it is Gene being constantly pummeled during the game foreshadows his mock trial and interrogation later in the story as well.
Finny is the innocent in the novel, the one who truly cares for Gene and seeks his friendship Finny is incredibly easy-going, and several skills, including athletics and social skills, are remarkably natural for him. Others, like academics, are not so natural, and require great work to produce mediocre results. Finny is open & honest, and refuses to believe that Gene could betray him in any way. It is his gradual realization of this fact that leads to his second fall and tragic death.