First Sacred War participant Delphic amphictyony
The First Sacred War, or Cirraean War, was fought between the Amphictyonic League of Delphi and the city of Kirrha. At the beginning of the 6th century BC the Pylaeo-Delphic Amphictyony, controlled by the Thessalians, attempted to take hold of the Sacred Land (or Kirrhaean Plain) of Apollo, resulting in this war. The conflict arose due to Kirrha's frequent robbery and mistreatment of pilgrims going to Delphi and their encroachments upon Delphic land. The war, which culminated with the defeat and destruction of Kirrha, is notable for the use of chemical warfare at the Siege of Kirrha, in the form of hellebore being used to poison the city's water supply.  The war's end was marked by the organization of the first Pythian Games.