The return of authoritarian great powers, the slowing of the democratic wave, and outright reversion to authoritarian rule pose important questions for international theory. What are the implications of an international system populated with more autocracies? This question was posed by a diverse array of social scientists, public intellectuals, and policy analysts in response to the autocratic wave in Europe in the 1920s and 1930s. We show that a series of conversations emanating from quite diverse intellectual priors – from Christian realists to international lawyers and disaffected Marxists – converged on the risks these autocratic regimes posed to democratic regimes and the international order they sought to forge. These risks included unconstrained rulers, an inability to sustain international commitments and political processes that undermined rational deliberation at home and spread disinformation abroad. The reading of this work suggests an under-appreciated strand of liberal international relations theory, and these debates have direct implications for liberal arguments about the democratic peace. Rather than theorizing why democracies avoid war, they underscore the importance of understanding why authoritarian and democratic countries are particularly prone to conflict.

Preferences for conflict and cooperation are systematically different for men and women: across a variety of contexts, women generally prefer more peaceful options and are less supportive of making threats and initiating conflict. But how do these preferences affect states’ decisions for war and patterns of conflict at the international level, such as the democratic peace? Women have increasingly participated in political decision making over the last century because of suffragist movements. But although there is a large body of research on the democratic peace, the role of women's suffrage has gone unexplored. Drawing on theory, a meta-analysis of survey experiments in international relations, and analysis of crossnational conflict data, we show how features of women's preferences about the use of force translate into specific patterns of international conflict. When empowered by democratic institutions and suffrage, women's more pacific preferences generate a dyadic democratic peace (i.e., between democracies), as well as a monadic peace. Our analysis supports the view that the enfranchisement of women is essential for the democratic peace.

In recent decades a great deal of attention has been given to Kant’s writings on politics as presenting a possible path to lasting peace. In this literature too high an expectation is created over what Kant’s cosmopolitan thinking might achieve. Caranti’s book provides an excellent antidote to these speculations by spelling out clearly the implications of Kant’s peace theory. I suggest there may even be better ways for understanding the guarantee of perpetual peace, the role of religion and the ideal of the moral politician than Caranti maintains.

Is it joint democracy or state similarity that has a pacifying impact on interstate relations? This study explores the complementarity of the two propositions and demonstrates the potential of a particular kind of shared emancipative culture embracing values of autonomy, equality, choice, and voice to amplify the impact of joint democracy on interstate conflict. The data on cultural values, which comes from the World Values Survey, was integrated with the data from the Correlates of War Project to test the impact of joint democracy and cultural similarity on militarised interstate disputes (1981–2010). We find that culturally similar dyads are less likely to be involved in conflict with each other than culturally dissimilar dyads. Although, cultural similarity does not wash out the pacifying effect of democracy, it offers a complementary explanation to the democratic peace. We also find that states that are democratic and share higher than average scores on the emancipative values are less likely to engage in militarised interstate disputes than democratic states, which are culturally dissimilar or score low on the emancipative dimensions. This provides support for an additional normative/cultural impact on democratic peace.

Why has interstate war declined and why do states refrain from territorial conquests in the post-Second World War order? The 1928 Peace Pact cannot account for these remarkable developments. This article argues that outlawing war is not enough to promote international peace. International Relations debates on the influence of weapons of mass destruction, democratic regime types and political cultures on interstate behaviour provide further important insights into the delegitimation of certain types of war. Since the 1990s, a changing character of war and warfare has emerged that is especially promoted by democratic states. How democratic states have justified their military use of force and how they have conducted their military interventions has a strong and ambivalent impact on the liberal world order.

Do democratic dyads handle their disputes more peacefully than non-democratic dyads, or have they cleared the most contentious issues (that is, unsettled borders) off their foreign policy agenda before becoming democratic? This study compares the conflicting answers of the democratic peace and the territorial peace and examines the empirical record to see which is more accurate. It finds that almost all contiguous dyads settle their borders before they become joint democracies. Furthermore, the majority of non-contiguous dyad members also settle their borders with all neighboring states before their non-contiguous dyad becomes jointly democratic. Such findings are consistent with the theoretical expectations of the territorial peace, rather than the democratic peace. They also weaken a core argument of the democratic peace, for this analysis finds that one reason democratic dyads may handle their disputes more peacefully than non-democratic dyads is not because of their institutions or norms, but rather because they have dispensed with the disputes most likely to involve the use of military force prior to becoming democratic.

The democratic peace literature has convincingly shown that democracies do not fight other democracies. Theoretical explanations of this empirical phenomenon often claim that the citizenry in democracies prefers peaceful resolution of interstate conflicts. Still, there is a dearth of studies exploring the public’s preferences and values directly. We seek to rectify this by investigating, in a novel way, the relationship between regime type and citizens’ bellicosity. A comprehensive multilevel research design is employed, with data spanning 72 countries over the period of 1981–2008. This enables us to test one of the theoretical mainstays of the democratic peace thesis, viz., that regime type helps shape individuals’ attitudes toward war-fighting. Our results lend special support to normative democratic peace theory: Citizens of democracies are significantly more pacifistic than citizens of non-democracies. This result upholds when we rigorously control for other relevant factors, including specific characteristics of individuals and rival theoretical explanations.

We show that without a few peculiar modeling choices that are not justified by the core assumptions of the theory, selectorate theory neither unambiguously predicts the democratic peace nor that leaders of more inclusive regimes will rely upon the provision of public goods to remain in office, though they may be more likely to provide club goods. We illustrate these claims using relatively simple models that incorporate the core assumptions of their theory, while avoiding modeling choices we believe to be less appropriate. We argue for a revised version of selectorate theory, one that continues to emphasize the importance of the size of the winning coalition, yet we believe it provides a more realistic picture of democratic politics.

The Democratic Peace research programme explicitly and implicitly presents its claims in terms of their potential to underpin a universal world peace. Yet whilst the Democratic Peace appears robust in its geographical heartlands it appears weaker at the edges of the democratic world, where the spread of democracy and the depth of democratic political development is often limited and where historically many of the purported exceptions to the Democratic Peace are found. Whereas Democratic Peace scholarship has tended to overlook or downplay these phenomena, from a critical materialist perspective they are indicative of a fundamental contradiction within the Democratic Peace whereby its universalistic aspirations are thwarted by its material grounding in a hierarchical capitalist world economy. This, in turn, raises the question of whether liberal arguments for a universal Democratic Peace are in fact hollow promises. The article explores these concerns and argues that those interested in democracy and peace should pay more attention to the critical materialist tradition, which in the discussion below is represented principally by the world-system approach.