Reversal of magnetization in square‐loop metallic tapes is described in terms of the domain geometry and the dependence of this geometry upon the applied magnetic field wave shape. For a steady field whose amplitude is slightly greater than the coercive force, the reversal is accomplished by growth of a single axial domain originating at the thin tape edge. For steady fields of much greater amplitude, the reversal domain grows in from all tape surfaces. Because of the finite nucleation time required to establish the reversal domain, short duration, high amplitude field pulses can be used to investigate the mechanism of nucleation of the high field reversal domain configuration. A model which accounts for the nucleation process is suggested. The compatability of this model with various experimental results is presented. From these results an understanding of the high field reversal‐domain configuration and the kinetics of the nucleation and growth of these domains in lamellar materials is obtained. An auxiliary result obtained is the value of the ``intrinsic mobility'' of a domain wall which for a 65 Permalloy specimen is determined to be about 100 cm/sec oe.