92 WORLD POLITICS Nationalism can be defined as a political principle that demands that the unit of governance and the nation should be congruent.It replaces the principle of dynastic sovereignty on which agrarian empires were based.28 Whereas the unit of governance is usually understood to be the sovereign state,the nation is imagined as a community of common origin and shared historical destiny.29 In the modern era the introduction of the principles of national- ism-that ethnic likes should rule over ethnic likes-has led to waves of political mobilizations and a subsequent transformation of the state system.30 The ensuing ethnonationalist struggles have taken on a va- riety of forms:conflict over access to state power between the leaders of competing ethnic communities,31 secession from existing states in order to establish a new state ruled in the name of a particular ethnic group32 or to join another state controlled by ethnic kin,33 and competi- tion between new states over mixed territories inhabited by members of their respective ethnic core groups. While this literature helps to explain the broad historical and po- litical circumstances under which we can expect ethnonationalist mo- bilization and conflict,it is much less concerned with identifying the precise mechanisms through which such ethnonationalist mobilization turns violent.Only recently have a number of scholars turned to study- ing nationalist mobilization and conflict in greater detail.35 We selec- tively draw on this scholarship in order to develop our own model of ethnonationalist conflict. Our analytical point of departure is Tilly's polity model,which fea- tures a political system comprising a government and a number of con- tenders seeking to maximize their access to executive power.s6 Members of the polity enjoy a privileged position,while those excluded from direct access to government represent potential challengers(see Figure 1).Adapting Tilly's model along the lines proposed by Cederman and Girardin,we assume that polity members and challengers consist of ethnic groups and their leaders(including politically irrelevant groups 28 Gellner 1983. 2 Anderson 1991. 30 Kedourie 1960;Breuilly 1994;Brubaker 1996;Cederman 1997;Wimmer and Min 2006. For example,Brass 1991;Wimmer 2002. 32For example,Hechter 2001. 3 For example,Weiner 1971. 3For example,Brubaker 1996. 3For example,Beissinger 2002;Cederman 1997,chaps.7,8;Hechter 2000;Olzak 2006;Wim- mer 2002,chap.3. 36Ty1978.92 world politics Nationalism can be defined as a political principle that demands that the unit of governance and the nation should be congruent. It replaces the principle of dynastic sovereignty on which agrarian empires were based.28 Whereas the unit of governance is usually understood to be the sovereign state, the nation is imagined as a community of common origin and shared historical destiny.29 In the modern era the introduction of the principles of national￾ism—that ethnic likes should rule over ethnic likes—has led to waves of political mobilizations and a subsequent transformation of the state system.30 The ensuing ethnonationalist struggles have taken on a va￾riety of forms: conflict over access to state power between the leaders of competing ethnic communities,31 secession from existing states in order to establish a new state ruled in the name of a particular ethnic group32 or to join another state controlled by ethnic kin,33 and competi￾tion between new states over mixed territories inhabited by members of their respective ethnic core groups.34 While this literature helps to explain the broad historical and po￾litical circumstances under which we can expect ethnonationalist mo￾bilization and conflict, it is much less concerned with identifying the precise mechanisms through which such ethnonationalist mobilization turns violent. Only recently have a number of scholars turned to study￾ing nationalist mobilization and conflict in greater detail.35 We selec￾tively draw on this scholarship in order to develop our own model of ethnonationalist conflict. Our analytical point of departure is Tilly’s polity model, which fea￾tures a political system comprising a government and a number of con￾tenders seeking to maximize their access to executive power.36 Members of the polity enjoy a privileged position, while those excluded from direct access to government represent potential challengers (see Figure 1). Adapting Tilly’s model along the lines proposed by Cederman and Girardin, we assume that polity members and challengers consist of ethnic groups and their leaders (including politically irrelevant groups 28 Gellner 1983. 29 Anderson 1991. 30 Kedourie 1960; Breuilly 1994; Brubaker 1996; Cederman 1997; Wimmer and Min 2006. 31 For example, Brass 1991; Wimmer 2002. 32 For example, Hechter 2001. 33 For example, Weiner 1971. 34 For example, Brubaker 1996. 35 For example, Beissinger 2002; Cederman 1997, chaps. 7, 8; Hechter 2000; Olzak 2006; Wim￾mer 2002, chap. 3. 36 Tilly 1978