One use of a rhetorical device is repetition,which is used when he is saying "We must fight! I repeat it,sir,we must fight!" By saying this he is emphasisingor trying to to get the point through meaning that if you want to be free,then you must fight.
Another rhetorical device that he uses is hypophora,which is used when he is saying " Can gentlemen assign any other possible motive for it? Has Great Britain any other possible motive for it? Has Great Britain any enemy enemy in this quarter of the world call for all this accumulation of navies and armies? No, sir, she has none."
Hope this helps!
-kaitlyn