When war challenges civilian survival, what shapes the balance between normative and instrumental rationalities in survival practices? Increasing desperation and uncertainty can lead civilians to focus on their own material interests and to violate norms in the name of survival or gain—to the detriment of the war effort and of other civilians. Do norms, boundaries against transgressions, and considerations of collective interests and identities persist, and, if so, through what mechanisms? Using diaries and recollections from the 872-day Blockade of Leningrad (1941–1944)—an extreme case of wartime desperation—this article examines how three forms of cultural embeddedness shape variation in the strength of norms against calculative, instrumental rationality. Proximity and empathy with others, the structure of norms and analogies to legitimate instrumental practices, and reflexivity vis-à-vis war and others’ response interact dialectically with the war context to shape variation in violating norms and rationalizing transgressions. Theft of food and cannibalism, which involve tactics of survival or gain that also risk the well-being of victims (theft) or violation of a powerful taboo (cannibalism), demonstrate the weakness of norms on the margins but their power when core norms or other real, visible individuals are threatened.