The transition-period exception to the democratic peace asks whether, how, and under what institutional conditions a regime transition toward democracy raises a state's risk of armed conflict. Mansfield and Snyder theorized that incomplete democratization — mass political participation introduced without institutions capable of channeling it, such as effective constraints on executive power — creates incentives for elites to play the nationalist card and elevates the risk of both interstate and civil war. The external-war evidence for this claim has been progressively undermined: Narang and Nelson showed the statistical association is fragile (few weak-institution incomplete democratizers ever enter war, and the result depends on the Ottoman Empire's pre-1918 dismemberment), and subsequent work shows findings flip with measurement choices. The civil-war association is more robust but its mechanism is unresolved. Most recently, Boldt (2026), using matching and difference-in-differences, finds democratic transitions reduce interstate conflict on average — a sign reversal — while the institutional conditions (sequencing of executive constraints, liberties, and elections; state capacity; endogenous versus imposed transitions) under which risk rises remain established only through case studies such as Andersen's Scandinavian-exception program. The problem — the causal sign, the institutional conditions, and the operative mechanism, across conflict onset, participation, and sub-war aggression — remains open.

Background

The democratic peace — the empirical regularity that pairs of consolidated democracies almost never fight wars against one another — is among the most robust findings in international relations, but whether it extends to states in the midst of regime change has been contested since the mid-1990s. Mansfield and Snyder argued, across a series of studies (1995, 2002, 2005), that states undergoing incomplete democratic transitions — regime change that opens mass political participation, above all competitive elections, before complementary institutions such as effective constraints on executive power, professional state administration, and rule of law have developed — are unusually likely to become involved in war, both interstate and civil. The proposed mechanism is that rising and declining elites, facing newly mobilized mass publics but weak institutions, play the 'nationalist card' to rally popular support against domestic and foreign rivals. Democratization is typically measured with indices such as Polity (a composite of expert codings of authority traits, including executive constraints and the competitiveness of political participation) and, more recently, V-Dem (Varieties of Democracy, a disaggregated expert-coded dataset covering elections, executive constraints, civil liberties, and suffrage from 1789 onward); 'incomplete democratization' denotes partial movement on such indices without consolidation, and 'anocracy' denotes the mixed-regime middle of the Polity scale. Armed conflict is usually measured with the Correlates of War (COW) project's datasets on interstate wars and militarized interstate disputes (MIDs), which record uses or threats of force below the war threshold — the register of 'sub-war aggression'. The empirical status of this transition-period exception remains unsettled. Narang and Nelson (2009) showed that the claim that incomplete democratizers with weak institutions are more war-prone is not supported by the data: observations of such states actually participating in war are few, the statistical association between incomplete democratization and war depends entirely on the dismemberment of the Ottoman Empire before World War I, and results are sensitive to coding choices between war onset and war participation and between Polity composites and subcomponents. Bogaards (2010) and Bernhard, Örsün and Bayer (2017) reinforced the measurement critique, showing that how democratization is conceptualized and operationalized drives testing outcomes. On the civil-war side the evidence runs the other way: Hegre, Ellingsen, Gates and Gleditsch (2001) and, with an explicit period-detection algorithm, Cederman, Hug and Krebs (2010) find that democratization episodes robustly raise the risk of governmental (state-targeting, as opposed to territorial) civil-conflict onset, even controlling for regime level — although Vreeland (2008) showed that part of the mixed-regime effect in this literature is an artifact of how Polity codes its components, and Cervellati and Sunde (2014) treat violent democratization as a critical juncture shaping long-run growth. In their 2009 reply, Mansfield and Snyder concede the data problems but restate the theory and pose questions they leave open: how to disentangle the state-failure mechanism from democratizing nationalism (their example is internationally imposed elections coinciding with state collapse in Iraq), and whether attempted democratization without prerequisite institutions consolidates a durable pattern of illiberal politics rather than liberal democracy. A parallel policy debate concerns institutional sequencing: Carothers (2007) argued against the claim (advanced by Mansfield and Snyder, 2007) that institution-building must precede elections; the exchange was never settled empirically. Andersen (2020), using V-Dem for 1789–2018, found that Scandinavia's democratizations were unusually peaceful specifically in the dimensions of executive constraints and civil and political liberties, while the peaceful exception is less clear for the competitive-elections and suffrage dimension — suggesting the ordering of institutional change may matter — and traced the mechanism to pre-democratic impartial state administration in process-tracing analyses (2023, 2025) — that is, within-case reconstruction of the causal sequence linking transition to violence or its absence from primary historical sources — that remain case-comparative rather than global causal tests. Most recently, Boldt (2026), using time-series cross-sectional matching and difference-in-differences — statistical designs that compare transitioning states with otherwise-similar non-transitioning states before and after the transition — finds that democratic transitions reduce international conflict on average, including fatal conflicts, attributing part of the pacific effect to constraining institutions and the incorporation of women's political preferences — a sign reversal relative to the belligerent-democratizer claim whose implications for the weak-institutions subset central to Mansfield and Snyder's theory, for civil-war onset, and for sub-war aggression remain unexamined.

Problem Statement

Does a regime transition toward democracy raise a state's risk of armed conflict — and if so, through what mechanism and under what institutional conditions? The literature leaves this question open along three linked dimensions, across the longest span of the historical record the data permit (V-Dem coverage begins in 1789): (i) the sign, magnitude, and credibility of the effect of democratic transitions on involvement in interstate war and in militarized disputes below the war threshold, distinguishing dispute and war initiation from mere participation, and on civil-war onset — net of confounding by prior state weakness, anticipated conflict, and reverse causality; (ii) which institutional conditions govern the direction of the effect — the strength and sequencing of executive constraints, civil and political liberties, and electoral/suffrage reforms; underlying state administrative capacity; and whether the transition is endogenous or externally imposed; and (iii) which causal mechanism accounts for the estimated pattern — elite nationalist mobilization under mass participation with weak institutions, state failure, or changed commitment and signaling capacity (the account on which stronger, more visible institutions make a state's threats and promises credible to foreign audiences and thereby stabilize crisis bargaining). The question keeps the natural scope of the underlying literature (conflict onset, participation, and sub-war aggression; both interstate and civil conflict) rather than a single outcome, case set, or measure. The demonstrated sensitivity of results to democracy-measurement and transition-window choices (Polity composites and subcomponents versus V-Dem dimensions) and to single episodes (such as the pre-1918 Ottoman dismemberment cases) is a documented difficulty of this literature that any credible design must handle. The average interstate effect already reported in the Background is not among the outcomes the cited works leave open; the effects for the weak-institutions subset central to Mansfield and Snyder's theory, on civil-war onset, and on sub-war aggression remain unexamined.

References

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