When and how many: The effects of third party joining on casualties and duration in interstate wars

Abstract

What makes some wars longer and more severe than others is an important question in international relations scholarship. One underexplored answer to this question is the role that third party joiners play in lengthening conflicts, especially those states that intervene militarily after a war's initial stages. This article argues that late joining complicates bargaining by adding new issues to the war and increases uncertainty about the relative balance of forces. Thus, more information will be needed to resolve the bargaining impasse. This means additional fighting and a longer war. This lengthening in turn increases the number of casualties. This is a distinct process from simply having more participants in a war from the outset as those participants would not add uncertainty in the same way that late joiners do since questions about how those participants affect the relative balances of forces would be answered just as quickly as if there were only two participants at the outset. These claims are supported by a non-proportional hazards model regression, a Cox proportional hazards regression, and an ordinary least squares regression using the Correlates of War interstate war dataset.

Which wars spread? Commitment problems and military intervention

“… 25. This is consistent with Shirkey (2012b), who finds that intervention lengthens wars rather than that long wars are more likely to prompt intervention. Combined with the results herein, this suggests that it is commitment problems which both prompt intervention and lengthen wars. …”

“…Levy (2011) cites Russia’s determination to join Austria in a war against Prussia prior to the outbreak of the Seven Years War (1756–1763) as a prominent example of this. Other ante-bellum decisions to intervene include the French intervention in the War of Italian Unification (1859), Italian involvement in the Seven Weeks War (1866), and British and French participation in the Suez Crisis (1956) (Shirkey, 2012b).…”

“…Military intervention matters for theory as explanations of wars should be able to explain not only their causes and termination, but also why they sometimes draw in additional states and how they are fought. From a practical standpoint, the question matters as interstate wars which experience military intervention are longer and deadlier than those that do not (Shirkey, 2012b;Slantchev, 2004). While substantial progress has been made on which states are more likely to intervene (Altfeld and Bueno de Mesquita, 1979;Richardson, 1960;Siverson and Starr, 1991;Valeriano and Vasquez, 2010) 1 and when they are likely to do so (Joyce et al, 2014;Melin and Koch, 2010;Shirkey, 2009Shirkey, , 2012a, far less is known about which wars are likely to draw in outside states.…”

Indirect Interventions in Civil Wars

“…From this perspective, the focus lies on the intervening country and its relationship towards the target country. A further academic strand explores the effects of interventionism (Shirkey 2012(Shirkey , 2016. Typical questions in this area relate to the duration (Regan 2002;Balch-Lindsay et al 2008) and severity of the civil war (Sousa 2014;Wood et al 2012) once third states are caught in the dynamics of civil wars.…”

Power, Preferences, and Balancing: The Durability of Coalitions and the Expansion of Conflict1

“…However, while the United States built a coalition that did not provoke outsiders to come to Iraq’s aid, the Soviet Union saw the fruits of its cooperation with the Afghan government diminished by third‐party balancing. If fearful observers balance against a coalition, as Pakistan did, they can undermine the gains of multilateral action, such as capability aggregation and burden‐sharing, by draining the coalition’s resources, lengthening wars, drawing in still more participants, and increasing casualties (Shirkey 2012). Coalitions, like individual states, thus face a problem of committing not to take undue advantage of their collective power (cf.…”