This thesis is a systematic examination of causal factors behind ethnic secessionist conflicts in the post-Soviet space. It identifies potential causal variables, correlates them with a series of conflicts occurring in the former Soviet Union since its dissolution, and develops a model of ethnic secessionist conflict with four levels of conflict intensity, ranging from simple ethnic heterogeneity to de-facto independence of the secessionist entity. The model is then used to describe three pairs of secessionist conflicts each occurring in three different former Union Republics: Georgia (Ajaria vs. Abkhazia/South Ossetia), Russia (Tatarstan vs. Chechnya) and Moldova (Gagauzia vs. Transnistria). In each pair (a dual example in the case of Abkhazia and South Ossetia), there is a marked difference in the intensity of the conflict, with the former in each pair being successfully kept within the host state through essentially no use of violence, while the latter in each pair involved all-out war with the host state. The thesis combines Brubaker’s Triadic Nexus Theory (as developed by Laitin and others) with the ethnic cohesion argument to develop a two-part, four level framework of analysis. The difference between the first and second levels of conflict (simple ethnic heterogeneity vs. secessionist mobilisation) is described as the result of contrast between the identity cohesion of the minority and titular ethnicities at the time of the Soviet collapse. It is found that a greater ethnic cohesion on the part of the minority group (often as a result of “ethnic revival” occurring around the collapse) allows mobilisation before the host state can react to suppress, and therefore allows the formation of a secessionist movement. The third and fourth levels involve armed conflict or at least the threat of violent struggle (successful reintegration vs. de-facto independence). Unlike simple mobilisation, armed resistance on the part of minority groups in the former Soviet Union relies on outside support as a chief factor, with the difference between the two levels being the amount of external support received compared with the ability of the host state to react (and which may also receive external support itself). Once a group’s cohesiveness is enough to overcome the host state’s attempts to prevent mobilisation, and if outside support is sufficient, it can keep the host state at bay and join the ranks of de-facto states. This model shows how ethnic cohesion and its variations over time can influence mobilisation, as well as the influence of overt and covert support from outside actors in the formation of secessionist entities. The analytical framework adds to the fields of secessionism and conflict study, as well as provides research into several rather under-studied areas of the former USSR.