This chapter focuses on the work of Anna Freud and Dorothy Burlingham with young children exposed to trauma, losses and separation from parents. First we describe the concept of a psychoanalytically informed school in Vienna, the Hietzing school. Later, at the Hampstead nurseries Freud and Burlingham described in great detail the reactions of children exposed to those traumatic situations and losses, making recommendations on how to understand their behavioral manifestations, difficult emotions and how to help them. They take a psychodynamic point of view, rather than a behavioristic one. Later on, we describe the concept of defense mechanisms and lines of development described by Anna Freud in their manifestations in children and adolescents, with case examples illustrating the manifestation of these processes.