Wars between Kingdoms

The mighty battles of high ranking cultivators are indeed awe inspiring and mostly what tales and songs are written about, but every realm has a role to play in the grand wars of nations. This is because while grandmasters can kill scores of mortals with a blow they most often have to worry about dealing with other grandmasters. The same hold true for masters and monarchs while warriors will most often be leading squadrons of apprentices into combat themselves.
As such wars become about positioning. Moving high levels cultivators about to keep your enemies monarchs and grandmasters occupied while your lesser armies seek openings to seize enemy fortifications and cities. Armies of mortals take a long time to move compared to a high level cultivator. So they need to be protected by their own grandmasters or risk destruction as they range further afield where their enemies response time is faster. But those friendly grandmasters can't move too far out of their own position or they'll expose openings on their own side. So wars tend to be slow nearly symbolic affairs as high level cultivators slowly move about while armies reposition around them.
Any losses in these mortal armies can usually be replenished swiftly, and grandmasters and above are hard to pin down to truly kill. So wars typically last years if not decades. They are more a matter more of showing enough dominance to leverage at the negotiating table than actually taking territory. Though this does mean that if several grandmasters, or worse a monarch, are killed, then most kingdoms will promptly surrender.