A Century of the Irish Border: Revisiting Militarization in the Post-Brexit Era

Since Irish independence in 1923, the border between Ireland and the United Kingdom has undergone periods of militarization and demilitarization; but has been effectively demilitarized since 1998. Amid increases in border conflicts worldwide, crucial questions emerge: What caused these periods of militarization and demilitarization, and why has the border sustained its demilitarized status, even with Brexit’s destabilizing effects? Will the border be remilitarized in the future? To answer these questions, I apply and test two international relations theories, structural realism and social constructivism. In the absence of publicly available data, I gathered and coded an original dataset of Irish border militarization from 1923-2023. Then, I compared this dataset with expectations from the structural realist and social constructivist frameworks. To test structural realism, I collected data on British and Irish relative military-economic capabilities from 1923-2023 to examine whether changes in relative capabilities preceded shifts in border militarization. To test social constructivism, I created a dataset on the formal recognition of British-Irish identities on the Irish island to consider if changes in group identity recognition by the governments preceded changes in border militarization. My tests reveal some support for the structural realist and social constructivist frameworks. I conclude with predictions and policy recommendations for the Irish border and consider the implications of my findings for other border conflicts.