Complex sentence: By the time of "World of Warcraft", the Alliance and the Horde are not engaged in all out war any longer, however they are still hostile towards each other and skirmishes between the two sides occasionally erupt.
Split into simpler sentences: By the time of "World of Warcraft", the Alliance and the Horde are not engaged in all out war any longer. However, they are still hostile towards each other and skirmishes between the two sides occasionally erupt.