Plutarch, Demosthenes
Bernadotte Perrin, Ed.

18. Philip, however, elated by his good-fortune in the matter of Amphissa,¹ surprised Elateia and occupied Phocis. This step drove the Athenians out of their senses: no one ventured to ascend the bema and no one knew what ought to be said, but perplexity and silence reigned in the assembly. Then it was that Demosthenes, and he alone, came forward and advised the people to cling to Thebes; and after giving them courage in other ways and buoying them up with hopes, as he was wont to do, he was sent with others as ambassador to Thebes. [2] Philip also, as Marsyas tells us, sent Amyntas and Clearchus of Macedonia, Daochus of Thessaly, and Thrasydaeus, to speak in opposition to the Athenians.

Well, then, the Thebans, in their calculations, were not blind to their own interests, but each of them had before his eyes the terrors of war, since their losses in the Phocian war² were still fresh; [3] however, the power of the orator, as Theopompus says, fanned up their courage and inflamed their honourable ambition and obscured all other considerations, so that, casting away fear and calculation and feelings of obligation, they were rapt away by his words into the path of honour. And so great and glorious was the orator's success seen to be that Philip at once sent an embassy and asked for peace, while Greece was confident and up in arms to aid Demosthenes for the future; [4] and not only did the Athenian generals assist him and do what he ordered, but also the Boeotarchs. He managed at this time all the assemblies of the Thebans no less than those of the Athenians; he was beloved by both peoples and exercised supreme power, not illegally nor unworthily, as Theopompus declares, but rather with perfect propriety.