The invasion was planned out in three separate waves.
A third of the army along with Grain and Gabriel, would mount the first attack on the Kingdom of Solice.
From there, Grain would take a small elite team with him to Crane.
His goal was to wipe out the entire kingdom himself, as it was in the center of the country and would be his new residence going forward. He would start by attacking the Dawn Guard HQ, assuming it was still a thing.
He still had the map of the whole kingdom in the system, making tracking down the HQ's location child's play.
Grain rode with Remus and the rest of the army, until reaching the giant waterfall. Where he then split off with Gabriel and their third of the army, to begin the invasion. Grain would lead with his group, while Gabriel would remain behind, making sure the rest of the army made it up the waterfall.
Once Grain and Gabriel managed to take Solice, Remus would occupy it and they would continue.