First Sacred War The First Sacred War ( 595 BC - 585 BC ) , or " Cirraean war " , was fought between the Amphictyonic League of Delphi and the city of Kirrha . The conflict arose due to Kirrha ' s frequent robbery and mistreatment of pilgrims going to Delphi and their encroachments upon Delphic land . The war resulted in the defeat and destruction of Kirrha . The war 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 . Justifications of war . In ancient Greece , Kirrha was a heavily fortified city which controlled access to Delphi from the Corinthian Gulf . Kirrha took advantage of its location to rob and mistreat pilgrims to the Delphic Oracle , to tax Delphi , and to steal land from Delphi , land considered sacred to Apollo . This behavior prompted many of the other Greek city - states to form the Amphictionic League , a military alliance dedicated to protecting Delphi , c . 600 BC . The League consulted the oracle for advice on dealing with Kirrha , and the reply was a call for total war . The members of the league vowed to completely destroy Kirrha and ravage the surrounding areas . To this they added a curse in the name of Apollo : that the soil should bring forth no crops , that the children of the women and livestock should be deformed , and that the entire ethnic group that inhabited the city should be eradicated . Siege of Kirrha . The leader of the attack was the Tyrant Cleisthenes of Sicyon , who used his powerful navy to blockade the city ' s port before using an allied Amphictionic army to besiege Kirrha . What transpired after this is a matter of debate . The earliest , and therefore probably most reliable , account is that of the medical writer Thessalos . He wrote , in the 5th century BC , that the attackers discovered a secret water - pipe leading into the city after it was broken by a horse ' s hoof . An " asclepiad " named Nebros advised the allies to poison the water with hellebore . The hellebore soon rendered the defenders so weak with diarrhea that they were unable to continue resisting the assault . Kirrha was captured and the entire population was slaughtered . Nebros was an ancestor of Hippocrates , so this story has caused many to wonder whether it might not have been guilt over his ancestor ' s use of poison that drove Hippocrates to establish the Hippocratic Oath . Later historians told different stories . According to Frontinus , who wrote in the 1st century AD , that after discovering the pipe , the Amphictionic League cut it , leading to great thirst within the city . After a while , they restored the pipe , allowing water to flow into the city . The desperate Kirrhans immediately began drinking the water , unaware that Kleisthenes had poisoned it with hellebore . According to Polyaenus , a writer of the 2nd century , after the pipe was discovered , the attackers added the hellebore to the spring from which the water came , without ever actually depriving the Kirrhans of water . Polyaenus also gave credit for the strategy not to Kleisthenes but to General Eurylochus , who he claimed advised his allies to gather a large amount of hellebore from Anticyra , where it was abundant . The stories of Frontinus and Polyaenus both have the same result as Thessalos ' s tale : the defeat of Kirrha . The last major historian to advance a new story of the siege was Pausanias , who was active in the 2nd century . In his version of events , Solon of Athens diverted the course of the River Pleistos so that it didn ' t run through Kirrha . Solon had hoped to thus defeat the Kirrhans by thirst , but the enemy was able to get enough water from their wells and rainwater collection . Solon then added a great quantity of hellebore to the water of the Pleistos and let it flow into Kirrha . The poisoning then allowed the allies to destroy the city .