Fifty thousand soldiers waited for them on the border after being teleported by the arrays in Ilios. Despite being a land of warriors detached from technological advancement, Ilios still had runic and fuel carriages to transport its soldiers.
These fifty thousand soldiers were not everything that Ascent could gather. Ilios still had a hundred and fifty thousand soldiers stationed around its borders and major cities, ensuring this war would not be a chance for their enemies. Thus, Arthur has gathered the crumbs and leftovers from the nine commanders and none from the Imperial Army of Ilios.
However, the army could supply their carriages, flying vessels, wind ships, and other modes of transport that would allow the military to move as one. Thus, the most challenging step was to teleport such a large number, and it was done.