Demosthenes mistakenly sailed too early and landed at Siphae, where his plans were betrayed by a Phocian named Nicomachus.

Eventually, Hippocrates arrived in Boeotia with 7,000 Athenian hoplites and 1,000 cavalry, they were accompanied by 10,000 Metics and other non-citizens,[note 2] and began to fortify the temple at Delium.

Pagondas of Thebes, the commander of the Boeotian forces, urged them to attack anyway because he knew that the Athenians would eventually return and use Delium as a base for further invasions.

As Thucydides reports, the Boeotian left wing was surrounded and close to defeat, and only the Thespian contingent stood its ground.

[3] It is thought the incident occurred in part because no "state" shield devices were in use, which did not seem to have become general until the Second Battle of Mantinea, fought in 362 BC between the Thebans and the Spartans (and each side's allies) [1].

The Boeotians constructed a strange device, which, according to the description in Thucydides (4.100), seems to have been a kind of flamethrower and used the weapon to set fire to Delium and chase away the Athenians.

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.

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.