Sengen Base was a research station on Io established by United Europe in the early 21st Century. It was destroyed by a surprise Japanese attack when the two nations went to war over mining rights in the asteroid belt. Most of the 70 inhabitants were killed but Renée Messier and Alec Hall survived because they were away in a crawler on a geological expedition. On realizing what happened, the two headed for Loki Station but were pursued by two armed Japanese crawlers.