An overview of the fundamentals of ground target recognition using SAR has been given. There is a tendency, when discussing ground target ATR, to consider only the most complex problems consisting of very many target classes and challenging clutter environments. However, it should be borne in mind that radar ATR is not a single problem that can or cannot be solved but that it is a continuum of problems of varying degrees of difficulty and complexity all of which provide useful military capability. This was essentially the viewpoint articulated by the NATO SET111 Task Group on ground target recognition at the conclusion of that activity. Operational radar ATR systems already exist and the overarching challenge is to push forward the solution space to achieve successful operation in more difficult and complex circumstances. To achieve this, a number of key specific challenges must be overcome, some of which are identified and discussed in Chapter 10, and to a large extent it is these challenges that current researchers are tackling. Hopefully this book will inspire those reading to contribute to the effort to solve these challenges.