I don't know who got the funny ideas that there were no ground force in Logh - which we call Army today. That Senior General( I forgot his name), who got captured by Reinhard in the CIVIL war, was an officer from the army. If you don't know who he is, well, he is the one got sent back and shot dead by his peers for treason. Then there are some ground battle in Logh, like Yang had to put down the rebellion in the civil war. He did it on the surface of the planets. Attacking a Fortress require ground forces too. And I don't recall the Empire land their ships on the planet. The only time they land ships in Odin, they landed in the lakes. In the real world, or the one that runs under feudalism, you can get a knighthood, then fight in some battle. If you are lucky enough, and your king likes you, he will raise you to an Earl. And that is how it goes.