ORIGINAL: witpqs
Allow Upgrade plus be in a friendly base.
To upgrade the TOE must be in Rest mode, Allow Upgrade, be in a friendly base, command HQ within (I think it is) twice it's distance thingy.
The base the unit is present at has to have adequate supply too.
And then there's the matter of devices in the pools...
Combat squads upgrade by sending the current squads to the pool and drawing squads that have the weapons abstracted in the upgraded squads' values for anti-armor and anti-soft -i.e. they go to the pools with rifles and maybe one BAR per squad, and they come out with some rifles but more Thompson SMGs, grease guns, bazookas and rifle grenades. The men are still the same. Once you start the first sets of squads upgrading the process runs quickly with replacements happening every turn (if conditions are right).
No matter how bad a situation is, you can always make it worse. - Chris Hadfield : An Astronaut's Guide To Life On Earth