Rouketopolemos (Greek Рουκετοπόλεμος, literally Rocket-War) is the name of a local traditional event held annually at Easter in the town of Vrontados (Βροντάδος) on the Greek island of Chios. As a variation of the Greek habit of throwing fireworks during the celebration of the service at midnight before Easter Sunday, two rival church congregations in the town perform a "Rocket War" by firing tens of thousands of home-made rockets across town, with the objective of hitting the bell tower of the church of the other side. The rockets are wooden sticks loaded with an explosive mixture containing gunpowder and launched from grooved platforms.
The two rival parishes are St. Mark's and Panaghia Ereithiani, the respective churches built on two hilltops about 400 meters away from each other. Direct hits on each belfry are supposedly counted on the next day to determine the winner, but each parish invariably claims victory over the other. The result of this apparent disagreement is that both parishes agree to settle the score next year, and the rivalry is thus perpetuated. The church buildings themselves and the nearby buildings have to be extensively boarded up and protected with metal sheets and mesh for the occasion. Several Vrontadites regularly express their dismay at the explosive nature of the custom, but it is a source of significant tourist revenue for the area.
The origin of this event is unclear, but local tradition holds that it goes back to the Ottoman era. According to local lore it was earlier performed with real cannons, until Ottoman authorities prohibited their use in 1889.
There are many videos online that can be found displaying this event. An example of this can be found here