This introduction frames the entire series of guidance notes "Improving food security and nutrition in protracted crises – guidance to implement the CFS-FFA", providing background on protracted crises and the Framework for Action for Food Security and Nutrition in Protracted Crises (CFS-FFA) and also presenting the objectives of the series. Protracted crises are situations in which a significant proportion of the population is acutely vulnerable to death, disease, and disruption of livelihoods over a prolonged period of time.