How does the author present the theme of guilt and redemption in the novel, Dog Years?

Grass asks how a race, or nation, can free itself from its collective guilt, and disturbingly seems to imply that such things as the trials of war criminals are analogous to Matern's journey. No matter how many war criminals are punished, the dead will not be brought back and the punishers cannot be purified from the taint of their own passivity. Grass questions what redemption is possible years later, whether the guilt passes to their children, and how a nation frees itself.