The concept of a currency war is truly bizarre, but that's the modern world.
In such a "war," countries try to outdo each other in DEBASING their own currencies. In doing so, the quite openly RIP OFF the common citizen, for the benefit of large exporting countries.
In what way are the commoners ripped off? By the fact that their debased currency buys less and less, ESPECIALLY from foreign countries that don't debase as much.
A currency war is the ultimate "race to the bottom," with all parties striving to cheapen their currency as much as possible.
The tipping point will be when smart traders stop accepting certain currencies. Why should they, when they know those currencies will be worth less tomorrow than they are today?