Phoros

In Ancient Greece, phoros (Greek: φόρος) was the name for the membership dues paid to Athens by the members of the Delian League, formed to offer protection from Persian forces. It could be paid in military equipment (such as triremes) or money, most usually the latter. Consequently, a great deal of funds was paid to Athens for the purpose of military initiatives. Athens increased its military forces, resulting in its becoming a dominant and wealthy power.

References

• Buckley, Terry (1996). Aspects of Greek history, 750-323 BC: a source-based approach. Routledge. pp. 189–199 Chapter 10. ISBN 978-0-415-09957-8. 
• Powell, Anton (2001). Athens and Sparta: constructing Greek political and social history from 478 BC. Routledge. pp. 13–57 Chapter 1. ISBN 978-0-415-26280-4.