PREOCCUPIED WITH MILITARY STRATEGY AND THE glory of war, the Sontarans traditionally make little time for excursions to Earth. They have visited for a number of reasons: advanced battle research, minor elements of a greater objective, or simply having to make an emergency landing.
However, by the time their war with the Rutans reaches its five thousandth decade they are desperate to increase their numbers to all-conquering strength. In search of a planet that can be turned into a massive generator for cloned warriors, they realise that Earth presents just such an opportunity.