Due to a deteriorating security situation that is characterized by instability and unpredictability, Swedish authorities have been instructed to resume their civil defence planning. However, because such planning activities were discontinued in Sweden at the end of the Cold War, there is a considerable knowledge gap today in regard to the idea of a new civil defence - what this concept means today, and how it should be developed. The Swedish Defence Research Agency (FOI) has received several requests and commissions to conduct research and analyses in this area in recent years. In this report we discuss some of the fundamental challenges that the development of a new civil defence will have to respond to, both in the short term and in the long term. Following a brief historical overview of Sweden's total defence during the Cold War, the report presents a knowledge model for the current and future total defence. Connecting different types and levels of knowledge, the model essentially illustrates a need to identify threats as well as ways to counter these threats. The model also relates to research areas in which FOI contributes or could potentially contribute, with knowledge and analyses. Finally, this report presents a conceptual draft for a future civil defence, developed in a way that would deliver a comprehensive total defence.