Well, yes,
Miggy, I knew I could have googled it or even looked it from the books, but I thought it fairer to go by what I remembered. Anyway, I do not mean that it was wrong to give the thread to
Nerwen in any way since she knew it and obviously the name itself was the difficult part of the question, not realising what you were talking about. (By the way, I had a slight and eerie hunch that
Nerwen will come to the thread and post the actual name of the battle and just see what happened...

)
Anyway, no, I have absolutely no clue what
Nerwen is talking about right now

but I might as well guess.
The Battle of the Five Armies*, mayhaps? In a way it would fit the description, but it sounds a little far-fetched...
*see, at least I knew this one's name and didn't say something like "The Battle at the end of TH"