During World War II, the attention of higher allied military staffs was drawn to a problem which had assumed unexpected proportions. This problem was, in broad terms, the application to military operations of principles of hydrology and river hydraulics through the creation of artificial flood waves and inundations. Although accounts of artificial flooding may be found throughout recorded history … the use of such techniques generally remained a relatively minor factor measured in terms of the campaigns as a whole. The usefulness of the moat during the siege of a feudal lord’s estate during medieval times was, perhaps, for this type of small-scale military action, an exception.