Name of poem quoted By Sean and Miss Munro of a battle Irish vs Danes?

My mind often goes back to that scene where Sean and Miss Monro are quoting from a poem about a battle between Irish and With the Danes,if I remember right are coming up the hill they were looking down. Would love to find a copy of that poem,and it's name,with all the words that Sean and She didn't get to mention.
Slainte,Liam

ALL problems can be solved with the proper application and amount of explosives!