The Tyrriann forces were nearly completely revived. Most had unplugged and had their consciousnesses restored. Bundled neatly with their minds the tens of millions strong forces had had combat and survival training coded in during the restoration process. In addition, every soldier in the Tyrriann forces had recieved survival and training directly related to this planet. Preceding this main invasion small scout forces had been visiting the planet for years, pilfering weapons and equipment where they could and observing and learning about the planet. Should any soldier need to co opt weapons from any earthly resistance. they would be able to use them.
This has such a creepy vintage vibe, really cool