[Mobhack]

In SP games, whoever is left after casualties to other commanders becomes the new leader. It remains that way through the campaign, as and until the new commander gets destroyed of course. There are no rules to say that a subordinate needs to be of a lesser rank, either - so a replacement company commander may be an Lt with a platoon of his under a Major.

The "0" element is only guaranteed to be the leader for scenarios or stand-alone battles. That is why the HQ screen has the command details in there (P for platoon commander, C for coy).

Cheers
Andy