Also sometimes referred to as the "Prush-Antiford War".
Tensions between Antiford and The Prush Empire had been rising steadily since the early 1870s. Harold II and the VonKresser family had managed to keep the peace. In 1874, Harold II died, leaving his son, Harold III, heir to the throne. Harold III was a very different man from his father. He was short tempered and swift to take violent action.
Desiring control over the resources in the Prodigious Canyon, Antiford declared war on the Prush Empire on the 10th of Firch, 1879. The conflict was bitter on both sides.
In 1883, Antiford was in a stalemate with the Prush Empire. Both sides were evenly matched. The nation's engineers were inventing at an amazing pace and being stifled by the politics of the time. The King attempted to court the engineers, however, it was understood that it was simply a way to obtain new technologies to try and win the war.
Both nations destabilized into revolutions, see Antiford's and Prush's, and a treaty was signed calling for a permanent cessation of hostilities and officially, neither nation has a recognized claim to the canyon. This is an internationally-recognized document and also states that only people who live within the canyon, such as the city-state of Conwell, can claim political right to it.