I will admit there is a lot of divided opinion on this.
There seem to be two thoughts on this
1 It is the Wizards will that has been imposed upon the soldier, therefore if he is out of game off board or zero points so killed/knocked out. He will not be able to impose his will, soldier released.
2 It is an enchantment, soldier therefore still needs to shake it off.
but this also begs the questions:
1 Is it easier, maybe his will +roll against the basic spell level?
2 Does he move mindlessly, like a creature on the table?
3 Does the spellcaster's player still control the soldier?