This article offers a critical reappraisal of the Maoist state’s response to the 1954 Yangzi Floods. It uses a variety of sources, including previously classified government reports and oral history testimony to challenge the official narrative. Far from being a remarkable victory for the new government as it was portrayed at the time, the flood precipitated a humanitarian catastrophe that took almost one hundred and fifty thousands lives. Government hydraulic policies were partly to blame, as the vast majority of disaster victims were located in rural areas that engineers flooded deliberately by opening sluice gates. In addition to revealing the true scale of the flood, this article also uses the disaster as a prism to examine the early Maoist state. The government’s combative environmental policies turned disaster governance into a war on water. This approach had certain benefits, particularly in terms of organising an effective urban relief campaign. Unfortunately, rural policies had fostered an atmosphere of distrust, which encouraged many villagers to resist government policies. Ultimately, the flood revealed the profound impact that a political context can have upon the outcome of an environmental hazard.