Didn't the Iraqi's have the 4th largest army in the world at this time?
They got that big because they had just gotten done fighting an enormous war with Iran two years before. The pre-1980 army wasn't anything like the post-1988/89 one.
The army was inflated through conscription, and what they knew how to fight were setpiece defensive battles and step-by-step attacks. The kind of things you'd see in World War I. Literally World War I, actually, since against Iran they'd be attacking out of trenches while their artillery was lobbing gas shells.
The officer corps was basically Baathists and nothing but, since Saddam needed loyalists after the purges he'd made. Though I'm sure some of the other Arab militaries wouldn't be much better (the Saudi National Gaurd springs to mind), what they do have is a unity of purpose once they start going in a certain direction.