Paris plunged into darkness in air - raid exercise . With a heavy heart , to the ominous sound of wailing sirens , the City of Light plunged into darkness tonight , as Paris staged itsd first major air - raid exercises / dress rehearsal of the future drama of war . As cars and pedestrians halted in their tracks and lights flickered out like a dying candle , one light remained in the darkened city - the perpetual flame on the tomb of the Uknown Soldier - the one who died so that there should never again be war ... The exercises consisted in the treatment of supposed victims of a gas attack , in the extinguishing of incendiary and gas bombs and in the use of gas shelters . General staff officers surveyed the proceedings from the ground , while airplanes zoomed overhead , to measure the extent to which the city became invisible . Photo shows ; a gas " victim " being taken to a a first aid station by a rescue squad on the steps of the School of Medicine of the University of Paris . 16 October 1936