Court Marshall for Demotion?

Hi,

I was wondering if you had to be court marshalled to be demoted.

My grandfather served in the 3429th Ord MAM Co. (and at some time in the 423rd Inf. in '45), and held the rank of T-SGT, but was discharged a PFC.

Was it common for people to be demoted, say before going overseas or something like that?

And besides the OMPF (fire of '73), would there be any information, say in unit histories, morning reports, etc. that would give some indication of the event?

Thanks again!
Ken Buechele