"Battle Phyle", in Wikipedia.
The Battle of Phyle was fought between Athenian exiles who were seeking to restore democracy to Athens and a Spartan garrison trying to protect the oligarchic Thirty Tyrants. In the battle, 700 Athenian exiles under Thrasybulus decisively defeated the Spartans and their Athenian cavalry in a dawn ambush.
After the defeat of Athens in the Peloponnesian War, the Spartans led by Lysander imposed a government known as the Thirty Tyrants, which exiled many citizens. These exiles gathered at Thebes under the leadership of Thrasybulus, crossed to Attica and occupied Phyle, a suburb of Athens. The Thirty tried to disloge these exiles from Phyle, but were driven back by a snowstorm to Athens.
Before engaging the forces of the Thirty Tyrants in the Battle of Phyle, Thrasybulus, in his exhortation to his 700 soldiers, used the occurrence of this snowstorm as an omen that the gods were now fighting on their side. […]
This unexpected defeat shook the confidence of the government at Athens, and the Thirty began shortly afterward to prepare a refuge for themselves at Eleusis by seizing and executing a number of potential dissenters there. The exiles, meanwhile, received a great boost in prestige from the victory, and new recruits swelled their numbers rapidly. Just a few days after the battle at Phyle, Thrasybulus led a force of 1000 men to Piraeus. There, he won another victory, after which the Thirty fled to Eleusis. A stalemate then ensued, with Thrasybulus and his men holding the Piraeus while a new oligarchic government held Athens; this was brought to a close when a Spartan force under Pausanias arrived; after fighting an inconclusive battle with the men from Phyle, Pausanias arranged a settlement that restored democratic governance to Athens.