History of the Peloponnesian War

And when Phrynichus learned betimes that Astyochus was working to injure him and that a letter from Alcibiades about these matters had all but come, he anticipated it by himself informing the army that the enemy intended, seeing that Samos had no walls and that not all the ships were anchored inside the harbour, to attack the camp; he said that he had certain information of this, and that they ought to fortify Samos as quickly as possible and keep a watch upon everything. Now he was general, and was within his powers in acting thus on his own authority.