This article reviews the historical contingency of theory and practice in conflict engagement. World War II and the Cold War produced adversarial, distributive, competitive, and scarce resources conceptions of negotiation and conflict resolution, as evidenced by game theory and negotiation practice. More recent and more optimistic theory and practice has focused on party needs and interests and hopes for more party-tailored, contingent, flexible, participatory and more integrative and creative solutions for more than two disputants to a conflict. The current challenges of our present history are explored: continued conflict in both domestic and international settings, the challenge of “scaling up” conflict resolution theory and the problematics of developing universal theory in highly contextualized and diverse sets of conflict sites. The limits of “rationality” in conflict resolution is explored where feelings and ethical, religious and other values may be just as important in conflict engagement and handling.