In 479, he was re-elected "strategos", and given special powers as commander of the Athenian forces at the Battle of Plataea; he is also said to have suppressed a conspiracy among some in the army. He so won the confidence of the Ionian allies that, after revolting from the Spartan admiral Pausanias, they gave him the chief command and left him with absolute discretion in fixing the contributions of the newly formed confederacy, the Delian League. His assessment was universally accepted as equitable, and continued as the basis of taxation for the greater part of the league's duration. He continued to hold a predominant position in Athens. At first he seems to have remained on good terms with Themistocles, whom he is said to have helped in outwitting the Spartans over the rebuilding of the walls of Athens.