For every outrageous Spanish fiesta, there’s a historical explanation of sorts. This battle traces back to a 13th century border dispute between Haro and its neighbours in Miranda de Ebro. The king stepped in and ordered Haro to mark it’s border with crimson banners every Saint Peter’s Day and the first Sunday of each September. The observation of Saint Peter's Day broke down in celebration some 400 years later, in a joyous wine sharing turned into a purple shower. This happy celebration really caught on during the last century and was officially dubbed the Battle of Wine in 1965.