That would have been 1984, a full 14 years later.

Nope, you're talking about the full breakup. First antitrust court case described as "leading to divestment" ended in 1974. Look at wiki, that's where I verified it before I posted.

Do you have a link to that?

After reading more, it looks like the case and plan was filed in 74, then not decided until 82, then implemented in 84.

Still, I didn't realize it had started that early, so thanks for the trail.