The initial Greek force, some 600 Athenians led by Meletios Vasileiou, was soon augmented by volunteers from Aegina, Hydra, Cephallonia and Kea to ca.

A handful of Ottoman soldiers managed to break through the siege, and went to Karystos in Euboea to request the aid of the local governor, Omar Bey, and of the general Omer Vrioni.

The Greek rebels scattered before them, and the Ottoman forces entered Athens on 20 July.

Vrioni remained in Attica to pursue the Greek forces, while Omar of Karystos returned to his home province.

In spring 1822, the Greek forces were reinforced with artillery commanded by French Philhellenes, under Olivier Voutier, who began a bombardment of the fortress.