Battlestar Galactica is set in a distant star system, where a civilization of humans lives on a group of planets known as the Twelve Colonies of Kobol. In the past, the Colonies had been at war with an android race of their own creation, known as the Cylons. With the unwitting help of a human scientist named Gaius Baltar , the Cylons launch a sudden sneak attack on the Colonies, laying waste to the planets and devastating their populations. Out of a population of several billion, there are about 50,000 human survivors; most were aboard civilian space ships that were not near the initial attacks. Of all the Colonial Fleet, the Battlestar Galactica (an older ship about to be decommissioned and turned into a museum) appears to be the only military capital ship that survived the attack. Under the leadership of Colonial Fleet officer Commander William "Bill" Adama and President Laura Roslin , the Galactica and its crew take up the task of leading the small fleet of refugee survivors into space in search of a fabled thirteenth colony known as Earth.