Can you disband?

[Taqwus]

Take an astrally powerful commander, give him a ring of water breathing, then have him gateway the troops into an environment they can't survive. Doesn't work for amphibious troops, but for that... well, try an undead commander holding a Rod of the Leper King to disease 'em all. Eventually they should die unless you're Pan under Gift of Health and they're lucky with the recuperation.