Some World War I clinicians related the symptoms of traumatized servicemen to an underlying dissociation of their personality, consisting of two prototypical conditions: one involving functioning in daily life (inspired by Myers, whose work is also discussed in this article, and which will be labeled apparently normal part of the personality [ANP]) and one involving fixation in the traumatic experience and related attempts at defense (emotional part of the personality [EP]). These authors described two dissociative patterns. As illustrated in this article, one pattern consisted in the presentation of a dominant ANP suffering from constant or frequent intrusions from EP. The other pattern consisted in repeated complete alternations between ANP and EP. Instead of the use of purely symptom-oriented approaches, for the dissociative symptoms to be really resolved, an integration of traumatic memory in the personality, that is, between EP and ANP had to take place. These clinicians used hypnosis to access the traumatic memory and EP and to foster such integration; they agreed on the importance of the quality of the therapeutic relationship in this regard. However, they differed in opinion and practice as to the need to assists patients in their expression of traumatic emotions during this process. When the trauma was related merely to war experiences, such therapeutic processes took place within a simple phase-oriented treatment model, while in the presence of a history of previous trauma and related dissociation of the personality, this model had more complex applications. This is similar to modern treatment approaches of the sequelae—such as a complex dissociative disorder—of chronic (childhood) traumatization.