Apart from the obvious reasons Alpheo had listed when arguing against dismantling the military, there was one fundamental reason that made him see demilitarization as the absolute last option: they were on the brink of something great.
In most of the battles Alpheo had commanded, victory had hinged on the discipline and training of his soldiers—qualities that were meticulously drilled into them under his leadership. At Saracena, his troops would have run at the first sight of cavalry, but the trust they had in their officers made them persevere. And this was rewarded by victory.