That made zero sense. So MC left 5 troops in the castle like an idiot, but that means he had a force of 45 3rd advancements vs 42 or less who are also weaker than MC's soldiers (they were really ambiguous with where all the soldiers were. Lauel said he blocked several routes, so their forces would've been smaller than 42). The fight should've ended significantly faster and MC could've just sent half the soldiers back to reinforce the castle while he charged forwards with the rest and took their castle. He also could've won or forced a draw by never leaving the castle.