Yes, you're right. It was the St Crispin's Day speech from Henry V that Henry delivered to his troops before the battle of Agincourt.
Henry was, of course, a Welshman, born in Monmouth castle. Most of the much-vaunted 'English' archers were Welshmen from his home county.
Still, we can't let facts get in the way of a bit of patriotism!