are developmentally unprepared to experience and process. However as we grow up, this shielding cuts us off from our full range of feelings, even when we are now emotionally able to handle the feelings." Challenge to the defenses represents an exhortation to the patient to abandon the defense: "Again you smile when I ask you about feelings in relation to being humiliated by your husband. If you don't smile, how were you truly feeling?" This particular intervention is a very powerful one in the therapist's arsenal. As with all powerful interventions, if it is misapplied, the consequences can be severe: rapid misalliance with the therapist, worsening of symptoms, and treatment dropout. This is because the patient perceives a premature challenge, applied when a defense has not been clarified, as a criticism or a personal attack. A common misunderstanding of ISTDP is that the therapist's role is to badger the patient through the use of Challenge. However, the proper use of challenge is as an aid or enhancement to the therapeutic alliance by removing an obstacle to the rise in complex feelings with the therapist. If challenge originates as a product of frustration in the therapist or as a misunderstanding of the unconscious, then stalemate is virtually assured. The main purpose of challenge is to remove any obstacles in the way of the mutually agreed upon task of getting to the engine of the patient's present difficulties: warded-off, complex feelings in relation to traumatizing experiences with important attachment figures in the past. The majority of patients are able to experience their true mixed feelings with a combination of Pressure and properly clarified Challenge. However, a sizable minority of patients erect a massive wall of resistance with the therapist. This wall is erected automatically and is an over-learned, habitual response, used to avoid emotional intimacy, both with the therapist and with other important figures in the patient's personal orbit. When the therapist observes that the patient's resistance has fully crystallized, it is time to deploy the ultimate intervention. III. Head-on collision: Pointing out the reality of the defenses and encouragement to overcome them The Head-on Collision is an intervention aimed not at any single defense but rather aimed at the entire defensive structure being deployed by the patient. It is an urgent appeal to the patient to exert maximal effort to overcome the resistance, and it takes the form of a summary