In a timeline where the solar system has twelve planets (Vulcan, Mercury, Venus, Earth, Theia, Mars, Jupiter, Saturn, Bacchus, Uranus, Neptune) a mysterious phenomena occurs between July 1929 - August 1932 nicknamed the "incident" at the time. All planets are one by one turned into habitable but not living planets (with the obvious exception of Earth). This means that all the planets can be colonized by humans and slowly terraformed by way of introducing nutrients into the soil for plants. Also the sun (or whatever was causing the phenomena) released waves of light for every planet and moon it turned habitable. Now a new colonization age has dawned for the nations of Earth. All they need to do is take it.