Description:The sound of cow bells signal the start of war. A battle rages through the streets of Greece's Galaxindi between rival gangs. Flying though the air-- tons of colored baking flour. It's a famous Greek custom called "Flour War" that marks the end of Carnival. The event dates back to 1801, when the town's people defied the Ottoman rulers occupying Greece by celebrating the forbidden carnival and painting their faces with ash.(1:36)