Quote Originally Posted by Aedilred View Post
It's probably worth mentioning too that for all that Rule, Britannia! sounds like an imperative to go and take over the world, it's not really about conquest, it's about freedom and independence. The lyrics are all about how Britain will always resist tyranny and fight for her freedom; the "rule the waves" implication being that GB is an island and invaders would have to come from across the sea, so for as long as Britain rules the waves her freedom is assured.

To put it in context, it was written during the height of absolutism in most of Europe, and was essentially a Whig anthem; it became popular when Bonnie Prince Charlie were trying to force a Stuart restoration (also the context in which God Save the Queen with its "smash the Scots" verse, was written).
I've read that the original meaning was imperative (and the British certainly obeyed!), but discussing that's a little out of my comfort zone.