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In page Pericles:

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In the spring of 449 BC[citation needed], Pericles proposed the Congress Decree, which led to a meeting ("Congress") of all Greek states to consider the question of rebuilding the temples destroyed by the Persians. The Congress failed because of Sparta's stance, but Pericles's intentions remain unclear.[13] Some historians think that he wanted to prompt a confederation with the participation of all the Greek cities; others think he wanted to assert Athenian pre-eminence.[14] According to the historian Terry Buckley the objective of the Congress Decree was a new mandate for the Delian League and for the collection of "phoros" (taxes).[15]