This is a short play (never performed), forming part of a commentary on the fragmental Old English poem "The Battle of Maldon". The play itself in my opinion is one of Tolkien's best pieces of writing: it is written in the "old heroic alliterative measure", at which Tolkien excelled, and this enhances the feel of the piece.
Definitely one of my top favourite works by Tolkien, and one which no Tolkien fan should be without.