Communication networks are exposed to a variety of massive failure events following from activities of nature, weather-induced disruptions, technology-implied problems, and malicious human activities. In this chapter, we first highlight the characteristics of these scenarios and discuss example failure events reported during the last three decades. Next, we explain the concept of network resilience and present an overview of major problems and related schemes further addressed in this monograph, concerning (a) measures and models for the analysis and evaluation of disaster-resilient networks, (b) techniques for design and update of disaster-resilient systems, (c) algorithms and schemes for resilient systems, and (d) advanced topics focusing, e.g. on emerging communication technologies.