Twelve Colonies of Kobol
The Twelve Colonies of Kobol is the human faction in Battlestar Galactica. In both the original series and the 2003 remake, the Twelve Colonies of Kobol are an alliance of twelve human colonies founded by the original human home world of Kobol, with a space fleet composed of large battleship/carriers called battlestars. In both continuities, the Twelve Colonies are suddenly wiped out by their enemies, the Cylons. Only a small civilian refugee fleet and a single battlestar, the Galactica, survive, and resolve to flee from the Cylons in search of the lost human colony, Earth. Other than that, the Twelve Colonies of Kobol in the two series feature stark differences.
In The Original Series
The Twelve Colonies of Kobol was led by a president, and defended by a fleet of battlestars. After a long war with the robotic Cylons, the president decided to sue for peace, with the encouragement of the ambassador to the Cylons, Baltar. In truth, though, Baltar was a traitor, and the peace talks were actually a trap set by the Cylons. Almost all battlestars were destroyed in the ambush, leaving the colonies open to invasion by the Cylons. The only surviving battlestar, the Galactica, leads a fleet of refugees in hopes of finding Earth. Later it is revealed that the battlestar Pegasus also survived, but shortly upon reunion with Galactica it is lost. The refugee fleet eventually finds Earth... and we would all rather forget that they ever did.
In the 2003 Reboot
The Twelve Colonies of Kobol was an alliance of human colonies governed by a complex system led by a president. The colonies were all technically in a single star system that was composed of four stars only 0.13 lightyears apart. The humans were responsible for the creation of the Cylons, originally meant for labor. The Cylons rebelled against their human masters, and a fierce war was fought, during which the first battlestars were made. After an abrupt withdrawal and peace negotiation by the Cylons, the Twelve Colonies had peace for fourty years, using the time to build up the Colonial Fleet. However, in this time the Cylons inflitrated the fleet with human-looking Cylons, implanting a virus into the computers of battlestars. The Cylons triggered the virus, causing all battlestars to shut down, then proceeded to wipe out the fleet and bomb the colonies. Again, only the battlestar Galactica survived, this time being an old battlestar that escaped the virus because its computers were outdated. The government of the Twelve Colonies is wiped out except for the minister of education, who then becomes president. She and Galactica's commander William Adama take charge of a civilian fleet in search of the lost colony of Earth, meeting up with the Pegasus along the way. Again, the fleet eventually finds Earth, and again, many viewers would rather forget they ever did.
Assessing the threat level of the Twelve Colonies in the original series is nearly impossible, as little is known about the colonies themselves, and the technological details from the Galactica are wildly inconsistent.
The Twelve Colonies of the 2003 series are much easier to evaluate. Technologically, the Colonials are hardly better than the modern world. Their ships are equipped with no advanced shielding or weapons whatsoever, instead relying on armor, nuclear missiles, and kinetic energy weapons. The only exotic technology the Colonials possess seems to be FTL jump drives, which enables instantaneous jumping across distances of many lightyears, and artificial gravity. Territorially, the Twelve Colonies are on the small side, with only one star system and twelve planets. With regards to industry, the Twelve Colonies were able to produce and maintain a fleet of around 120 battlestars, each over a kilometer long, in the course of 40 years. The Galactic Empire would consider the Twelve Colonies of Kobol an insignificant power, and the United Federation of Planets would consider it a minor power, though an extremely primitive one.