The Viper (Mark I) was introduced into Colonial service shortly before the outbreak of the first Cylon War. However, it was the Mark II Viper series, designed specifically for use with the new Colonial Battlestars, that is best remembered. The Mark II was used during the Cylon War, proving a capable fighting vehicle. It is regarded as one of the reasons the Twelve Colonies did not suffer defeat at the hands of the Cylons. The Mark II remained in service after the end of the war, with William Adama commenting that he last saw one, likely one of the last of its type, roughly twenty years after the end of the war.
The Mark II was superseded by the Mark III (Battlestar Galactica: Blood and Chrome) and later models, with the Mark VII serving in front-line duties forty years after the end of the Cylon War, as seen in Battlestar Galactica: The Miniseries. By this time the Viper design had progressively evolved, retaining the basic structural configuration (essential for use with Colonial Battlestars), but with variations in length, equipment, and capability. No information is provided about the intervening designs, but by the time the Mark VII was introduced the Viper design incorporated software-based controls and fully networked systems, providing superior agility, battle management, and flight information for the pilot.
The Mark VII was later upgraded to include Dr. Gaius Baltar's navigational software. Along with the majority of the Colonial Fleet, this software allowed the Cylons to remotely disable the Vipers during the renewed attack on the Twelve Colonies. The few Mark VIIs that survived the disaster were later stripped of this software. The older Mark II fighters, not equipped with the "fly-by-wire" systems of newer Vipers, were unaffected by the Cylon modifications to Dr. Baltar's program. Two squadrons of Mark IIs were present in the Galactica's starboard flight pod in preparation for the Battlestar's new role as a museum ship, and after the Galactica's Mark VII squadron was destroyed by the Cylons, the display of Mark II's were refitted for combat by Galactica's deck crew.
Along with a handful of surviving Mark VII's, the older vipers made up Galactica's fighter wing during the Cylon sneak attack, the Battle of Ragnar Anchorage, and most of the Galactica's action prior to the arrival of Battlestar Pegasus in Season 2 episode "Pegasus", when her ability to manufacture more Mark VIIs was added to the fleet. When the Pegasus was destroyed in Season 3 episode "Exodus: Part 2", her nearly intact squadrons, all of them composed of Mark VIIs, were transferred to the Galactica 's air wing. At the time of the episode "He That Believeth in Me" (season 4, episode 3), more Vipers were available than qualified pilots, and trainee pilots were used to fly the extra fighters.
During the Battle of the Resurrection Hub, Vipers of both types were deployed from the Rebel Basestar against the Resurrection Hub and its two basestar escorts. The Vipers were towed into battle with their engines and electronics cold, allowing them to get the element of surprise in the attack. In that battle, both Colonial Vipers and Cylon Heavy Raiders fought side-by-side against the Cylons and once D'Anna Biers was unboxed and rescued, the Vipers, each equipped with at least one nuclear missile, lined up and launched their nuclear missiles into the Resurrection Hub, destroying it.
The Viper is armed with multiple kinetic energy weapons. Both known models have weapon hard points for mounting missiles under the wings.
2 forward-firing 30mm mass accelerator cannons mounted in the wing roots, each with an 800-round ammunition capacity and a 20-round-per-second fire rate
1 forward-firing Lightning Javelin missile launcher in the belly, with an 8-round ammunition capacity
1 to 2 missiles (In "The Hub", the Vipers are equipped with nuclear missiles, which they use to destroy the Resurrection Hub. In "The Oath", a conventional missile was fired by Narcho at the President's Raptor in an attempt to destroy it, but the missile missed and hit the Rebel Basestar instead, causing minor damage.)