Climate Shocks and State Formation: The 1970 Bhola Cyclone and the Birth of Bangladesh

State formation through secession often requires two critical steps: building mass support for independence, and engaging in violent conflict against a state resisting territorial loss. Combining satellite data with archival sources, we statistically document how exposure to the 1970 Bhola cyclone in East Pakistan which killed 350,000 people led to a rise in separatist sentiments expressed in voting booths, and later induced citizens to take up arms against the government and engage in guerrilla warfare. We identify the cyclone as a focal point that helped galvanize dispersed separatist sentiments into an organized political movement and war, in part by revealing the Pakistan government’s indifference to Bengalis’ suffering. This important historical case identifies the specific causal channels by which a climate shock produces armed conflict (Hsiang et al., 2013).