The marking of ambulances and hospitals is a practice which goes back a long time, but until the middle of the nineteenth century different colours were used by different countries: Austria a white flag, France a red one, Spain and the United States yellow, to mention a few examples. The devices displayed were not generally well known, so that they were seldom respected: it frequently happened that artillery shelled ambulances, that grapeshot riddled the waggons bearing the wounded but displaying no outward sign that their mission was one of mercy.