In the eventuality of a nuclear weapon being used, which country is most likely to detonate it first?

First nuclear weapon detonate: which country is responsible for it Nuclear tests don't count, only actual weapon used for war or strategic purpose connecting to war. Update 2025-05-20 (PST) (AI summary of creator comment): The creator confirmed that a nuclear detonation under a 'last warning' doctrine would count. This includes scenarios such as: A single nuclear strike Intended as a communication strategy or to show resolve In response to an enemy threatening vital interests, even if the threat is through conventional means.