National Response Scenario Number One is the United States federal government's planned response to a nuclear attack. It is one of the National Response Scenarios developed by the United States Department of Homeland Security, considered the most likely of fifteen emergency scenarios to impact the United States. The Scenarios are related to the National Response Framework (NRF), which describes the structures and mechanisms of a response and the National Incident Management System (NIMS) that gives a framework to orchestrate emergency management.