Systemic change by means of hegemonic war amounts to a transformation of the parameters of political legitimacy. The war decides who rules and the content of legitimacy at the global level. As such, only the most extensive major-power wars – ones that end in a new phase of substantial capability re-concentration and global military-political and economic leadership – can be designated hegemonic wars. The history of international order and, therefore, of the Long Cycle started with the Italian renaissance and the West European maritime explorations of the late fifteenth century. I identify four hegemonic wars: the Italian Wars (1496–1559), the Thirty Years’ War (1618–1648), the French Revolutionary and Napoleonic Wars (1792–1815), and World War II (1939–1945). To this list, I add one “failed” power transition, the end of the Cold War (1989–1991). A new Long Cycle began in 1991, with the United States serving as the lone World Power. This chapter explores each Long Cycle and all four phases therein. This discussion is comparatively brief for the first two long cycles, becoming more extensive for the three most recent cases, for they offer more “usable pasts” than the earlier cycles from which to draw relevant lessons for modern times.