This chapter summarizes the main lessons for diplomacy that we derive from our study. These eight lessons are: 1. A major factor separates the crises that escalate to war from those that do not; in the latter, a strong leader reins in any hard-liners who advocate going to war. 2. Individuals make a difference. 3. Contingency plays a more important role than system structure in determining whether or not a crisis escalates to war. 4. Someone must stand for peace. 5. The secret to preventing war structurally is to find a functional equivalent to war. 6. Norms and rules are important for avoiding war – and, therefore, maintaining peace. 7. War can be avoided; it is not inevitable. 8. The realist concepts of the national interest and balance of power do not always accurately describe the behavior of states.

The Eastern Crisis is a nonwar case that occurs during the heyday of the Concert of Europe. Nevertheless, the major powers avoided war with one another not because of the Concert’s deliberations, but rather because of domestic politics within France. King Louis-Philippe reined in his hard-line prime minster, Thiers, thereby removing the threat of war. This indicates that domestic politics is more important than system structure, at least in this case. One major lesson we can derive from this case is that “someone must stand for peace” – that is, one way for actors to avoid war is for a strong leader to rein in domestic hard-liners.

This chapter provides an insight into the role of systems science for sustainability assessment. In the first part, we present seven axioms that have been derived from system-theoretical perspectives and show their relevance for sustainability assessment. Following these axioms, we propose a way to structure and analyse systems following four system characteristics: (1) system boundary and interactions with the external environment; (2) purpose, goals, and associated decision-making drivers and criteria for the system; (3) system structure (subsystems, elements, and their interactions), dynamics, and emerging behaviour; and (4) system information, outcomes monitoring, and learning. These four characteristics were applied to study, first, the historical development of the energy system analysis and, second, an Australian urban systems-transformation initiative. The systems-analysis framework presented provides a good basis for putting the elements of a system analysis into their broader context, and designing purposeful interventions. Especially for more transformational change, the alignment of stakeholder values, institutional arrangements, and available knowledge become key leverage points.