The peace that came at the island of Vytal was not one that was reached easily. It was rather, the last resort; peace between the nations...or human extinction.
The war that lead up to it could certainly be considered TOTAL. The kingdoms had been involved in wars before, certainly, but nothing of THIS scale.
The four large and many smaller kingdoms began the fight thinking that the fight would be done by the end of the year; instead, it dragged on, lasting first one, then two, and finally three years, each one becoming more brutal, horrific, and bloody than the last.
Dust weaponisation assured that fighting the war as wars had been in the past would only lead to massive death and horror for both sides, and putting it to perfect use (something the kingdom of Mantle did with horrifying efficency) ensured victory for its master.
The massacures of the war are well known...the aborted invasion of Mantle’s southern coast by Vale and Vacuo, stopped dead in its tracks by Fort Danse and her 40 cannons. Mantle’s troops being exposed to unrefined Dust and falling where they stood, perfectly preserved, when Mistral attacked. The bloody trench warfare between Vacuo and Vale over the center of their continent. And of course...The Burning the unholy sharing of Dust, nuclear, conventional, chemical, biological, ionization and who knows how many other kinds of warheads that obliterated Mantle’s capitol city, destroyed the moon...and nearly killed everyone on Remnant.
When that happened...the nations came together, at Vytal, and swore to create a lasting peace.