war responsibility
Often refers specifically to Japan's responsibility for World War II, but can be used in broader contexts of accountability for war.
Debate over war responsibility continues even now.
He made a statement acknowledging war responsibility.
戦後補償 refers to postwar compensation or reparations, a concrete action, while 戦争責任 is the broader concept of moral or legal responsibility for war.
Compound of 戦争 (war) and 責任 (responsibility).