Compressively stressed thin films with low adhesion frequently buckle and delaminate simultaneously into telephone cords. Although these buckles have been studied for decades, no complete understanding of their propagation has so far been presented. In this study, we have coupled a nonlinear plate deformation with a cohesive zone model to simulate the kinematics of a propagating telephone cord buckle in very close agreement with experimental observations. Proper inclusion of the dependence of an adhesion upon the mode mixity proved to be central to the success of the approach. The clarification of the mechanism promises better understanding of buckle morphologies.