Democracy
Working paper PDF
Parties and the military are democracy’s two gatekeepers: when both exclude radicals, democracy should survive. Interwar Japan defies this expectation. Established parties held parliament and the military contained its radical faction, yet democracy collapsed. Radicals circumvented both gates by building civic organizations. Using monthly prefecture-level data on right-wing associations, I find that the May 1932 prime-ministerial assassination triggered a durable organizational surge in a peripheral region excluded from the governing coalition since 1868, concentrated in associations propagating party dissolution and direct imperial rule. Above this base sat a smaller metropolitan layer bundling officers across army divisions with civilian ideologues and peripherally radicalized civilians—under 5% of the right-wing universe but a third of all violence-supplying organizations. Cross-divisional bridging predicted violence supply where raw officer count did not. The coordination architecture was built before May 1932, sat outside the chain of command, and outlasted the army’s purge of its radicals.
State Formation and State Building
Under review PDF
Many influential theories of state development assume that political fragmentation enables subjects to exit across competing rulers, thereby disciplining extraction, yet direct evidence that fragmentation shapes how subjects resist remains scarce. I show this in Tokugawa Japan (1615–1868), where nearly 300 feudal domains generated sharp variation in villages’ proximity to rival rulers. In a difference-in-differences design, the shogunate’s conversion of domains to direct rule raised the probability of nearby mass exit by 4 percentage points with no rise in direct confrontation, and a grid-year panel confirms the pattern. Among revolting villages, greater access to outside rulers tilted resistance toward exit over confrontation. Domains more exposed to credible exit threats levied lower taxes, especially where neighboring domains could absorb migrants. The findings microfound a premise that load-bears across the Great Divergence literature, fiscal-federalism arguments, and the cartel theory of the territorial state system.
Working paper
While scholars broadly agree that feudal orders arose from the limitations of centralized state control, much less is known about the mechanisms through which this process began and unfolded—specifically, who fostered the fragmentation of state power and where it originated. I propose a theoretical framework identifying the conditions under which statebuilders deliberately hollow out their own administrative apparatus by privatizing extraction: granting fiscal immunities in exchange for a share of the returns. I evaluate the model’s implications using the case of early medieval Japan, where varying degrees of feudalization across regions can be systematically observed through estate commendations to the imperial court. Consistent with the theory, I find that estate commendation by emerging local warrior elites occurred most prominently in peripheral regions where central authority was weak but local administrative capacity remained strong.
Work in progress
Social scientists have argued that conflict and military technological innovation fostered the formation of territorial states. While the literature has predominantly examined European history, Japan’s Warring-States Period offers a unique context to test this claim; the island country initially composed by more than 100 autonomous local powerholders (daimyo) was exposed to an exogenous shock of military innovation, an accidental importation of firearms in 1543, after which the fragmented society rapidly transformed into a centralized state under a singular authority. Using original grid-year datasets of battles, castles, and territorial changes, we show (preliminary, descriptive) results suggesting that the technological shock diminished defensive advantage and made economic power better translate into battleground success, thereby inducing small rulers to concede their autonomy.
Work in progress
Although agricultural surplus was vital for early state formation, it also exposed states to external threats. I claim that while surplus itself jeopardized states, the administrative capacity to generate it—specifically hydraulic management—promoted state persistence. Maintaining costly irrigation systems provided rulers with bargaining leverage over both external predators and internal subjects, deterred both invasions and defections, and thereby fostered stable territorial control. I illustrate this argument through a formal model and test it using global data of historical polities since 3400 BCE. Duration analysis shows that states with greater hydraulic dependence, measured by the potential yield gap between irrigated and rainfed farming, tended to endure longer without losing territories, while higher absolute yields accelerated territorial loss. The result was exclusively found in earlier periods, where developing hydraulic systems was more costly. Additionally, polities with greater hydraulic dependence tended to develop more complex social structures.
International Relations
Pacific Forum Issues & Insights, Vol.22, pp.31–49
Book chapter in 国際関係研究の方法 (University of Tokyo Press, 2021)