I recently wrote a detailed summary of that event. The TL;DR is this:
The Alliance did not want to attack Vulpera, but they wanted to stop the transport of Horde War supplies. The fighting is between hired caravan guards and Alliance pyromancers. The Alliance is burning the caravan wagons, but they don’t have anyone in there, as noncombatants have been removed. However, to the vulpera, even though the Alliance isn’t attacking noncombatants, they are still burning the vulpera’s homes, and that’s almost as bad. There is no indication that the Alliance tried diplomacy or economic agreement.