[en] The subject of this paper will be Marshall Rosenbluth's contributions to and impact on the development of the free electron laser. Although in this paper the author has been able to describe only a few, Marshall Rosenbluth has made many important contributions to the free electron laser problem. A fuller list of his contributions would include the following: Tapered wigglers, Sideband instability, Resonant coupling between betatron and synchrotron oscillations, Analytic theory of transverse gradient wiggler, The gain- spread-transverse excitation theorem, Phase area displacement, Pulse build-up, Two-dimensional effects