Defeating leaders in campaign scenarios

[nukchebi0]

Are the units of a specific leader supposed to disappear immediately upon the defeat of their superior? I was under the impression that this was true, but when I tried Valley of Death earlier tonight, I was surprised to find that the swarm of wraiths from the Northern and Eastern liches were very much active. This completely destroyed my plan of quickly assassinating the two with GK/Paladin while focusing everything else on the SW lich, so I want to know if I remembered wrong or the game is glitching.

[TheScribe]

You're just remembering wrong. When a leader dies his units stay. Unless he's the last person on his team, or if the objective is to kill him. In which case when you kill them you win.

It's possible using WML to program for all a sides units to dissappear upon the leader's death. Maybe you saw one of those events and that's what gave you the wrong impression.