>>76946130At that point he just didn't fear the Giant: he hated it with a passion. He saw the Giant turn docile in front of him, and saw the general seeing it too - the Giant had just proved him wrong and ruined everything he had worked for. So he just wanted him killed and in his rage ordered the nuke.
And he regretted it afterwards, but not because he realized he was wrong, but because he was gonna get killed. Sure, a lot of people would freak like that too, but you could see in his pointless attempt to save himself that all this time he didn't care about his country, he cared about himself and himself alone.
