<P> To further strengthen Athens' grip on its empire, Pericles in 450 BC began a policy of establishing kleruchiai--quasi-colonies that remained tied to Athens and which served as garrisons to maintain control of the League's vast territory . Furthermore, Pericles employed a number of offices to maintain Athens' empire: proxenoi, who fostered good relations between Athens and League members; episkopoi and archontes, who oversaw the collection of tribute; and hellenotamiai, who received the tribute on Athens' behalf . </P> <P> Athens' empire was not very stable and after 27 years of war, the Spartans, aided by the Persians and Athenian internal strife, were able to defeat it . However it did not remain defeated for long . The Second Athenian Empire, a maritime self - defense league, was founded in 377 BC and was led by Athens . Athens would never recover the full extent of their power, and their enemies were now far stronger and more varied . </P>

What were some of the problems caused by the delian league