I know it's not mentioned in canon, but do you suppose it's possible that Dementors were used in the First War? Sirius did say: "...he had huge numbers at his command -- not just witches and wizards but all manner of Dark creatures..." so that does leave it a bit open. I wrote a story several years ago where Dementors attacked James and Lily, although no one ever questioned it. I'm curious, though, what others think here. And what other Dark creatures do you suppose Sirius might have been referring to?