This is a revitalised and reimagined version of the science-fiction warfare-based Battlestar Galactica (1978 series). The series ended with four seasons in 2009 and was continued by the 2012 series Battlestar Galactica: Blood & Chrome
In this series we follow a human battleship in deep space known as Battlestar Galactica. The ship is fleeing a relentless attack to wipe out the entire human race implemented by their own created AI beings known as Cylons. The Battlestar accompanies and protects what they assume to be the last 50,000 people in existence after a quickly executed genocidal attack on all 12 human colonies, in which the Cylons were almost completely successful. They occupied all colonies and killed any found survivors. With low supplies, no allies, and little hope, the entire convoy ventures into uncharted space to flee the onslaught in hopes of finding refuge among the stars. Their destination is the fabled 13th Colony of Earth, founded by a tribe said to have left the human origin planet of Kobol "early on" before any other tribes or the founding of the 12 colonies.
Battlestar Galactica continued from the 2003 miniseries to chronicle the journey of the last surviving humans from the Twelve Colonies of Kobol after their nuclear annihilation by the Cylons. The survivors are led by President Laura Roslin and Commander William Adama in a ragtag fleet of ships with the Galactica, an old but powerful warship, as its command ship. Pursued by Cylons intent on wiping out the remnants of the human race, the survivors travel across the galaxy looking for the fabled and long-lost "thirteenth" colony: Earth. Unlike most space opera series, Battlestar Galactica has no aliens (the antagonists are man-made Cylon robots), the primary armaments used by both military forces utilize bullets, rail guns, and missiles instead of lasers, and the series intentionally avoids technobabble. Instead, most of the stories deal with the post-apocalyptic fallout of the destruction of the Twelve Colonies upon the survivors and the moral choices they must make as they deal with the decline of the human race and their war with the Cylons. Stories also portray the concept of perpetuated cycles of hate and violence driving the human-Cylon conflict, and religion, with the implication of a "God" whose angelic agents appear to certain main characters (most notably Gaius Baltar).
Over the course of the show's four seasons, the war between the Colonials and the Cylons takes many twists and turns. Despite the animosity on both sides, the humans and a faction of the Cylons eventually form an uneasy alliance in the wake of the Cylon Civil War. The Cylon leader, humanoid Cylon "Number One", named John Cavil, precipitated the schism in the Cylon ranks. Cavil deceives the other models by obsessively hiding the identities and origins of the remaining five humanoid Cylon models, the "Final Five", who, known only to him, are a more ancient type of Cylon, created by a previous iteration of human civilization. Other plotlines involve the mysterious destiny of Kara "Starbuck" Thrace, who is the subject of a prophecy claiming that she is the "Harbinger of Death" who will "lead them all [humanity] to its end," as well as the redemption of Gaius Baltar through the Cylons' monotheistic religion, after he becomes a pariah within the fleet.
In the final episodes, a divinely resurrected Kara Thrace leads the surviving humans and their Cylon allies to a new planet, which Adama names "Earth". The first group of survivors settle in ancient Africa. The "real" Earth that the Colonials had searched for during their years in space was revealed in an earlier episode to have been originally inhabited thousands of years before by a previous form of humanoid Cylons. Ironically, these humanoid Cylons created their own Centurion robotic slaves, who waged a nuclear attack against their masters, devastating the planet and making it uninhabitable. The new Earth is found to be inhabited by early humans, who are genetically compatible with the humans from the Galactica and the rest of the fleet, but who possess only the most rudimentary civilization. Human beings had apparently evolved independently on both Earth and Kobol, the original home world of the humans who settled the Twelve Colonies.
The surviving humans and humanoid Cylons settle on the new planet; they discard all technology, destroying the fleet by flying it into the Sun, in order to postpone the creation of robotic servants until their society has progressed to higher ethics. The surviving Cylon Centurions are given possession of the remaining Cylon Basestar, and proceed to jump away from Earth. In the final scenes, modern-day Earth humans are shown to be descendants of the colonists, their humanoid Cylon allies, and the early humans.
At the end of the series finale, an angelic Baltar and Cylon Number Six (played by Tricia Helfer) are walking down a sidewalk in modern-day New York City. They are unseen and unheard by the people around them. As the two walk, they notice technologically advanced robots, computers, and other cybernetic devices, and they talk about the technological advancements the humans have made since the Colonists and humanoid Cylons first arrived to this Earth over 150,000 years earlier. Cylon Number Six and Baltar have an exchange over one of the ongoing themes from the series, "All of this has happened before. But the question remains, does all of this have to happen again?"