Military has two broad meanings. In its first sense, it refers to soldiers and soldiering. In its second sense, it refers to armed forces as a whole. The business of soldiering is as old as recorded history itself. Some of the most enduring images of the classical world portray the power and feats of antiquity's military leaders. And over the years, military units have come in all shapes and sizes. They have been as small as a handful of medieval peasants banded together for battle under their feudal lord or as large as the invasion force created in 1944 for D-Day. In our own era, world wars and countless other major conflicts have changed the political landscape beyond recognition.