he might then have made a poem , and told first of heavenfield , when oswald as a young prince against all hope won a great victory with a remnant of brave men ; and then have passed at once to the lamentable defeat of oswestry , which seemed to destroy the hope of christian northumbria ; while all the rest of oswald 's life , and the traditions of the royal house and its feud with that of deira might be introduced allusively or omitted .