What is, or should be, the role of defense in thinking about the justification of use of armed force? Contemporary just war thinking prioritizes defense as the principal, and perhaps the only, just cause for resorting to armed force. By contrast, classic just war tradition, while recognizing defense as justification for use of force by private persons, did not reason from self-defense to the justification of the use of force on behalf of the political community, but instead rendered the idea (...) of just cause for resort to force in terms of the sovereign's responsibility to maintain justice, vindicating those who had suffered from injustice and punishing evildoers. This paper moves through three major stages in the historical development of just war thinking, first examining a critical phase in the formation of the classical idea of just cause as the responsibility to maintain justice, then discussing the shift, characteristic of the modern period, to an idea of sovereignty as connected to the state and the prioritization of defense of the state as just cause for use of force, and lastly showing how this conception of the priority of defense became part of the recovery of just war thinking in the latter part of the twentieth century. The paper concludes by noting recent changes in thought on international law that tend to emphasize justice at the expense of the right of self-defense, suggesting that the roots of just war thinking imply the need for a similar rethinking of contemporary just war discourse. (shrink)