Free For All
A riot of war is where things go nuts. This is a melee! A free for all!
This is a jukugo word, which usually means on'yomi readings from the kanji. If you know the readings of your kanji you'll know how to read this as well.
That game was a free for all that we don't see very often.
A melee occurred in the audience due to Koichi's speech.
On the first day of the sale, the mall became super crowded, like it was some kind of battle royal.