The military, political, and social histories of Warring States China (471-221 BC), Sengoku Japan (1467-1603), and Early Modern Europe (1453-1816) were all incredibly similar, T. Greer reminds us:
The origins of all three “warring state” periods are found in the ruins of large empires whose collapse forced hundreds of smaller political units to take control of their own affairs. This was a time of “feudalism” or “fragmented sovereignty,” where politics was personalized, rulers did not exercise a monopoly on violence, and individuals had to navigate conflicting political loyalties. This situation did not last. Governments that once struggled to control the population they ruled and exercised power through the relatives or aristocratic peers of the ruling house soon commanded large and impersonal bureaucracies that directly extracted taxes from and conscripted the service of millions of people. Small aristocratic forces dominated by noble cavalry detachments were eclipsed by gigantic forces of massed infantry. Trade intensified, living standards increased, governments centralized, and most importantly, the number of states dwindled.
War does not create stronger governments so much as it selects for strong government through a rather Darwinian process.