Okay kiddo, so have you ever played a game where you are a soldier and you fight for a country or a group of people? Well, a mercenary war is kind of like that game, but in real life.
So sometimes, countries or groups of people don't have enough soldiers to fight their battles. They might not have enough money to pay their soldiers or maybe not enough people want to join their army. So what do they do? They hire mercenaries.
Mercenaries are like soldiers, but they are not actually part of any country or group. They fight for whoever pays them the most money. So if one country wants to fight another country, but they don't have enough soldiers, they might hire mercenaries to help them.
But here's the thing - mercenaries don't really care about the cause they are fighting for. They are just there for the money. So sometimes, they might switch sides in the middle of a war if they get offered more money from the other side. This can make things very confusing and messy.
And that's what a mercenary war is - a war where both sides are using mercenaries to fight for them. It can make things unpredictable and sometimes it doesn't end well for anyone involved.