Did you know?

I was watching QI on the BeeB yesterday and this interesting fact came up:- Aparently, in the whole history of our world, only once ever have two democracies declared war upon each other. Can you name the two democracies though?? Watch this space for the answer (or alternatively you could send some money to my Education Fund, the arrival of which I will celebrate, which in turn will loosen my tongue, and I’ll let slip the answer to you).