What are the exact requirements for officer promotions in XCom Long War

I found this page:
https://www.ufopaedia.org/index.php/Officers_(Long_War)

And it lists certain requirements, but not all of them. Many of my soldiers are grayed out when I try to promote them.

What are the exact requirements?

For example (I’m shooting in the dark here), do you need to be a Lieutenant before you can be promoted to Captain? The page above says "The officer must have been on at least 5 missions (3 by default with the Dynamic War second wave option) at his current officer rank." – how can I tell? Where is that information in the UI; or heck, I’ll even take where in the save file, which property?