What role does rhetoric play in the diplomacy of these events?

Watch the attached video—which portrays parts of Thucydides’ history of the Peloponnesian War (along with a great cameo by Socrates!). What role does rhetoric play in the diplomacy of these events? What insights does Thucydides offer about human nature? https://www.youtube.com/watch?v=SNcJ79qPIg8 Note: You can ignore the intro segment, which tries to tie Thucydides to the Gulf War.