A wise man once told Artemis that he may have dragons, but wars are won by men. Unless you would want to burn everything along the way. But if he were to win the upcoming war, he needed men to fight for him on land and that's why the gift his cousin bought to him was so important.
Since he had to send seventy thousand men to the Mines to help out his sister, House Arteides had men shy of thirty thousand soldiers bearing its sigil and carrying its banners. Although no one knew, but Artemis knew it very well that he needed men. With addition of ten thousand men from House Horris, Artemis had a total of thirty thousand. If the capital was to be ambushed right then and there, he would be defeated in just a matter of minutes.