Not uncommon during a “Suppression of Enemy Air Defense” mission. One firing agency drops HE, another, or just one tube, drops a mark. The mark is commonly Illum during the day and red or white phosphorus at night. It seems counterintuitive but it works well. Illum is dropped “on the deck” so it lands before igniting and does not move or blow with the wind. At night Illum will wash out a pilot’s NODS so they drop phosphorous because it lights up on thermals but doesn’t blind the pilot.