At any cost:how Ukrainians think about self‐defense against Russia

How do populations facing external aggression view the costs and benefits of self-defense? In Western countries, war support has been shown to follow cost–benefit calculations, resembling the moral principle of proportionality. A categorical position, in contrast, means supporting self-defense regardless of the costs. To evaluate which moral principle populations facing external aggression follow, we conducted a conjoint experiment with 1,160 Ukrainians in July 2022. We examine support for different strategies Ukraine could pursue against Russia, which vary regarding the political autonomy and territorial integrity they afford and three costs: civilian and military fatalities, and nuclear risk. We find that Ukrainians do not trade off autonomy or territory against these costs. A new method to rank conjoint-attributes, computing “nested” marginal means, shows that respondents categorically reject political or territorial concessions, regardless of costs. This provides first experimental evidence that populations resisting external aggression do not subject war outcomes to cost–benefit calculations.