In the spring of 449 BC, 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' intentions remain unclear. 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. 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).