Researchers at University of Florida shed some light on ant behaviour, including what happens after long battles they lead. Apparently, when two ant colonies are fighting, fighting changes the genetic make-up of victorious colonies. Furthermore, in some cases, fatal fights with thousands of casualties do not produce a distinct winner. Instead, colonies cease fighting and fuse together, with the queen of each colony still alive.
http://phys.org/news/2016-03-mortal-enemies-allies-ants.html
http://phys.org/news/2016-03-mortal-enemies-allies-ants.html