Battle of Delium The Battle of Delium or of Delion took place in 424 BC between the Athenians and the Boeotians , and ended with the siege of Delium ( also known as Delion ) in the following weeks . Prelude . In 424 BC the Athenian generals Demosthenes and Hippocrates planned to invade Boeotia . Demosthenes mistakenly sailed too early and landed at Siphae , where his plans were betrayed by a Phocian named Nicomachus . As Hippocrates had not yet arrived , Demosthenes could not attack and was forced to withdraw . Hippocrates eventually did arrive in Boeotia with an Athenian army and began to fortify the temple at Delium . After five days , the fortifications were complete , and Hippocrates set up a garrison and sent the rest of his army back to Athens . At the same time , the Boeotians gathered their army to challenge Hippocrates , but when they saw that the Athenians were leaving many of them thought it was pointless to attack . Pagondas of Thebes , the commander of the Boeotian forces , urged them to attack anyway , because he knew the Athenians would eventually return and use Delium as a base for further invasions . Battle . Pagondas moved his army into position near the Athenians , although both armies were hidden from each other by a hill . The Boeotians had 7 , 000 hoplite s , 1 , 000 cavalry , 500 peltast s , and 10 , 000 light troops . The right wing was formed by troops from Thebes , and the Thebans drew themselves up to a depth of 25 men rather than the usual 8 , the centre by men from Haliartus , Coronea , and Copiae , and the left wing by troops from Thespiae , Tanagra , and Orchomenus . They were later joined by the Locria ns . When Hippocrates learned of the Boeotian army , he joined the main Athenian force , leaving 300 cavalry behind at Delium . The Athenians had about the same numbers of hoplites and cavalry , but had fewer lightly armed troops , mostly from their allied cities . They lined up at the usual depth . Because of the asymmetry in deployment the Theban right wing would almost certainly be victorious , but also because of their deployment the Athenian hoplite line was longer and would outflank the Boetian left line . This unique deployment by the Theban general Pagondas explains the subsequent unfolding and progress of the battle . The Boeotians charged unexpectedly while Hippocrates was giving a speech to his men . The centre lines saw the heaviest fighting . As Thucydides reports , the Boeotian left wing was surrounded and close to defeat , and only the Thespian contingent stood its ground . The victorious Athenian line got into confusion as it circled round the Thespian contingent and surrounded it . Some of the Athenian hoplites fought and killed one another when they met at the other end , mistaking their countrymen for the enemy . This was history ' s first documented incident of fratricide ( Geoffrey Regan , " Back Fire " , Robson Books Ltd . , London , 1995 ) . It is thought the incident occurred in part because no " state " shield devices were in use , a practice which seems to have become general by the time of the Second Battle of Mantinea , fought in 362 BC between the Thebans and the Spartans ( and each side ' s allies ) . In any case , Pagondas sent his cavalry to support the Boeotian left wing and the Athenians were defeated in turn . Meanwhile , the Boeotian right wing was also victorious , and the Athenians fighting there fled ; when the Athenian centre saw that their two wings had been defeated they also fled . About 500 Boeotians and 1 , 000 Athenians had been killed , including Hippocrates . One of the Athenian hoplites in the battle was the philosopher Socrates . Plato has Alcibiades give the following account of the retreat of the Athenians at Delium , and Socrates ' own actions then : The Boeotians chased the Athenians until nightfall . Most of the Athenians returned to the fort at Delium , where a Boeotian herald announced that they were offending land sacred to the Boeotians and must leave . The Athenians replied that the land was now theirs and was now sacred to them , and that they held it in self - defense from the Boeotians , who were allies of the Spartans . Aftermath . For two weeks there was no action , but the Boeotians were joined by 2 , 000 hoplites from Corinth , as well as other troops from their various allies . The Boeotians constructed a strange device , which according to the description in Thucydides ( 4 . 100 ) seems to be a kind of flamethrower , and used this weapon to set fire to Delium and chase away the Athenians . Only about 200 Athenians were killed ; the rest were allowed to escape . After Delium had been recaptured , Demosthenes and his forces finally arrived , but the lack of communication between him and Hippocrates meant that his arrival was essentially useless . He landed near Sicyon , but was quickly defeated . In addition to showing an innovative use of a new technology , Pagondas made use of planned tactical warfare for one of the first times in recorded history . In the previous centuries , battles between Greek city states were relatively simple encounters between massed formations of hoplites , where cavalry played no important role and all depended on the unity and force of the massed ranks of the infantry , straining against the opponent . At Delium , Pagondas made use of deeper ranks , reserves , cavalry interventions , light - armed skirmishers ( peltasts ) and gradual changes in tactics during the battle . These novelties were to be later exploited in more famous actions of Theban troops in the following century , led by Epaminondas in the Battle of Leuctra and others .