How Human Boundaries Become State Borders: Radical Flanks and Territorial Control in the Modern Era

State-led attempts to expand their territory run directly into norms of "border fixity," norms of self-determination, and the high costs of conquest, which is why international conflict has rarely led to border changes since 1945. Radical flank groups—non-state organizations with extreme means and ends that are on the ideological and physical front lines of territorial disputes—turn each of these obstacles into advantages. By quietly shifting the demographic status quo and manipulating the security dilemma to inspire supportive "defensive" intervention, radical flanks create new human boundaries that become new state borders. Using original datasets of political violence and settlement construction, we analyze the Israeli settlement movement in the West Bank from 1967-present and reveal the power of bottom-up territorial change across time and space.