They Came from the Stars

From "... and the sky full of dust" blog:

The adventure itself is loosely based on an adventure my dad ran for us back when I was a young lad. We fought the Greenies, got sick from radiation poisoning, and won in the end (I think we drove them off). I made them the focus of a story I wrote, where they were greatly enhanced by battle armour with missiles and machine guns, killing off characters al over the place. Happy memories :)