🔍 The question and theory:

When and where do states coercively alter their internal demography? A theory is developed that predicts when states will change the demographic “facts on the ground” by resettling and expelling ethno‑national populations. The theory argues that, under particular scope conditions, states use demographic engineering to secure control over:

• nonnatural frontiers (border zones that lack natural geographic barriers), and
• areas populated by ethnic minorities who are co‑ethnics with elites in a hostile foreign power.

📊 New subnational data and causal strategy:

New subnational data from both China and the USSR are assembled to test the theory. The analysis exploits spatial variation in exposure to international conflict and uses a difference‑in‑differences design to causally identify the spatially differential effect of the Sino‑Soviet split (1959–1982) on demographic engineering.

📍 Key empirical findings:

• China: The Sino‑Soviet split led to a disproportionate increase in expulsions of ethnic Russians and resettlement of ethnic Han in Chinese border areas that lack a natural border with the USSR. Resettlement was targeted at areas with higher concentrations of ethnic Russians.
• USSR: The split also produced a significant rise in expulsions of Chinese and in the resettlement of ethnic Russians in Soviet border areas, with resettlement concentrated where Chinese populations were larger.
• Across both cases, demographic engineering took the form of both expulsions and state‑led resettlement, and these actions were spatially targeted in line with the theory.

📈 Why this matters:

These results advance political demography by showing that ethnic group concentration and cross‑border dispersion are endogenous to international conflict. This finding complicates existing literature that treats ethnic demography as an exogenous predictor of conflict and highlights when, where, and to whom states seek to effect demographic change during interstate rivalry.