The thesis, which is based on extensive archival materials, explores the origins of the on-going conflict between Armenia and Azerbaijan by focusing on the emergence of the first Armenian Republic in 1918 and its territorial issues with Azerbaijan, in order to understand the factors which led to this conflict. It examines the background to the creation of the first Armenian Republic by researching the location of the ‘historical Armenian homeland’, the construction and reconstruction of the notion of the ‘Armenian homeland’, the aspects facilitating the way in which the ideology and strategy of the Armenian national movement developed, and the factors instrumental in the construction of the Armenian identity. The work provides a historical background to the Armenian claims to Garabagh and Nakhchyvan and analyses the ethnic, historical, economic, geographical and security arguments used by the first Armenian Republic to substantiate its vision of the territorial delimitation between Armenia and Azerbaijan with regard to these regions at the Paris Peace Conference in 1919. The thesis also considers the positions of the external powers involved in the South Caucasus vis-à-vis the Garabagh and Nakhchyvan issues and assesses the impact of their stance on the settlement of these conflicts.