An RSC covering all of East Asia is a recurrent pattern. Before and during the Second World War, Japanese power and imperial ambition linked Northeast and Southeast Asia together into a single security region. Earlier still, periodic waxings of Chinese power also brought these two regions into the same security sphere. But before the rise of imperial Japan in the late nineteenth century, and during waning periods of Chinese power, Northeast and Southeast Asia sometimes had largely separate regional security dynamics. During the Cold War, the patterns of regional security in East Asia were heavily penetrated by, but not completely subordinate to, the two superpowers. Although somewhat masked by Cold War patterns, this chapter will tell their story as separate Northeast and Southeast Asian RSCs, albeit with some interregional crossover by China (Buzan 1988a, 1988b, 1994). After the Cold War, penetration from the global level diminished substantially and altered in form, and the regional level story is best told on an East Asian scale. That will be the approach of chapter 6.

In Southeast Asia, decolonisation produced a fairly typical postcolonial conflict formation. It was almost entirely composed of weak states, but since most of these had solid historical roots, a set of relatively durable modern states eventually emerged. Like that in the Middle East, this RSC quickly became heavily penetrated by outside powers. In Northeast Asia, only the secondary states (Korea and Taiwan) were postcolonial.