100 years ago the Irish stabbed us in the back because we were busy with WW I and ended up getting more of their own people killed than ours.
Edit: I've realised I should clarify, while I don't dislike the Irish, I'm somewhat bitter about their revolutions due to my family fighting in some of them and the fact that most forms of the Irish Republican Army are terrorists, and they're the ones involved in a lot of revolutions.