Board Thread:Suggestions forum/@comment-25869554-20160210171858/@comment-26149161-20160212115618

Dol Amroth coldn't do it simply because they didn't have enough numbers. Even then, they would have slaughtered many Haradrim before they fell. The Rohirrim were outnumbered, but not as much as the Swan Knights would be. 6,000 Swan Knights would have done just as well, maybe better, against the Haradrim forces.