- Brigadier General - Major General - Lieutenant General - General
Technically you're right.
But the implication is no woman would be promoted above him in the military hierarchy, so it would take a woman being elected commander in chief.
In 2008, General Ann Dunwoody became the Armys 1st Female 4-star General. But again, we can assume Jessup would retire before he'd stand for getting leapfrogged by anyone beneath him, let alone a woman.
Surely a four star General is the highest beneath the President
Sounds like you are asking about chain of command here, which is slightly different than rank.
Above four star generals but below president are:
The Under Secretary of the Army The Secretary of the Army The Under Secretary of Defense The Secretary of Defense
Note -- these positions could be technically held by generals or retired generals.