Fall of New Caprica
The takeover and occupation of New Caprica by a massive Cylon fleet and the retreat of the battlestars Galactica and Pegasus, as well as the remainder of the orbiting Fleet.
As his first action as the newly elected President of the Twelve Colonies, Gaius Baltar orders the permanent settlement on the planet, after using the argument of colonization to win the election over Laura Roslin.
Cylon agent Gina detonates a nuclear warhead aboard Cloud Nine, destroying it as well as least two smaller ships. Despite worries from the military that the nuclear attack could indicate a immediate Cylon strike, Baltar maintains his colonization order on what has become known as New Caprica.
One year later, conditions on New Caprica are severely deteriorated. Most people still live in tents, medicine and other resources are in short supply, and Baltar's government is corrupt and ineffective. Admiral William Adama and Commander Lee Adama, commanding the Galactica and Pegasus respectively, continue to orbit New Caprica along with other ships of the Fleet to provide defense. (The orbiting ships are presumed to be incapable of landing on a planet.) With many crew members having settled on New Caprica, many of the ships are falling into disrepair. Defenses are sparse: an effective CAP cannot be organized.
On the 380th day after colonization, a massive Cylon fleet, attracted by the nuclear detonation months before, suddenly appears within the nebula. Commander Lee Adama urges Admiral Adama to order the Fleet to jump, knowing that they cannot win in a firefight. Reluctantly, the Fleet retreats to an unknown location. As waves of Raiders and Heavy Raiders fly over New Caprica City, Caprica-Six, Sharon Valerii, and a Number Five copy enter President Baltar's office and indicates their intent to occupy the planet, and the colony. Faced with no choice, Baltar formally surrenders to the Cylons as waves of Centurions enter New Caprica City as a stunned population looks on.