The Fleet Landing Exercises, or FLEX were amphibious landing exercises conducted by the United States Navy and United States Marine Corps between 1935 and 1941. The purpose of these exercises was to formulate a workable amphibious warfare doctrine. The development of the necessary craft and other equipment, and the proper tactical deployment of them were also results. Finally, the exercises demonstrated the usefulness of a standing body of Marines, the Fleet Marine Force, specially prepared for amphibious expeditions.