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Fisk is a typical orders-only XO who generally keeps to the status quo established by his commanding officer. Like his counterpart on Galactica, Saul Tigh, Fisk is fond of drinking, although he appears far less likely to drink on duty than Tigh has in the past. He has a jovial personality, often cracking jokes to ease tension.
Serving in an unspecified role in Pegasus's CIC, then-Lieutenant Colonel Fisk is promoted to colonel and XO shortly after the Cylon attack on the Twelve Colonies, when Colonel Belzen is shot in front of the crew by Cain for refusing her order to send all of Pegasus's Vipers, outnumbered 4-to-1, into an attack on a Cylon communication relay. Shaken by this summary execution, Fisk is careful never to contradict the admiral, and orders the attack without hesitation.
Fisk relates an incident aboard a civilian ship to Colonel Tigh in confidence over drinks (Pegasus). He and Kendra Shaw lead a marine strike team onto the ship, the Scylla, to carry out an order to strip the vessel of select resources and personnel. When Fisk reports that the civilians refuse to cooperate, Cain tells him to shoot the family of any selectee who refuses to comply. Faced with an advancing crowd that grows angry and unruly, and with Fisk and the marines showing signs of faltering, Shaw follows Cain's example and carries out their threat, raising her pistol and shooting a woman in the head, sparking weapons fire which leads to the deaths of nine more. This effectively ends any resistance from the passengers and crew, and cows them into heeding the boarding party's demands (Razor).
After Commander William Adama and Admiral Cain come to the brink of an armed showdown between their respective battlestars over her summary convictions of Karl Agathon and Galen Tyrol, Cain orders Fisk to lead a contingent of Pegasus marines aboard Galactica, ostensibly to guard CIC in the event of an enemy boarding during the Battle of the Resurrection Ship. His orders are to have the Marines ready to "terminate Adama's command", i.e. assasinate Adama and the CIC senior staff, once the battle is over, on her command of "Execute case orange" (Resurrection Ship, Part I). After the battle, however, she decides not to give the order. A relieved Fisk lets out an unexpectedly loud belly laugh in response to Tigh's observation that he could use a drink, much to the confusion of everyone in the CIC (Resurrection Ship, Part II).
Colonel Fisk breaks up a violent beating of Helo and Tyrol in the brig, conducted by Pegasus Specialists Vireem and Gage. He dresses down the men, warning them that striking an officer on Pegasus has severe penalties, and sends them on their way. When thanked by Helo and Tyrol, Fisk summarily dismisses their thanks, adding that he owed Lieutenant Alastair Thorne his life, as did others on Pegasus; he broke up the beating more for the sake of the uniform than anything else. When Helo explains that Thorne was attempting to rape Sharon Valerii, Fisk says, "You can't rape a machine, Lieutenant."
Colonel Fisk later assumes command of Pegasus when Admiral Cain is killed by an escaped Cylon agent, Gina Inviere (Resurrection Ship, Part II). Appropriately, Fisk is promoted to the rank of commander.
Later, Fisk became involved in the Fleet's black market, using his resources as commander to allow the shuttling of black market cargo through Pegasus, including fresh "Caprican Imperial" cigars to Vice President Gaius Baltar, for which he received unknown benefits from the black market boss, Phelan. When Fisk tries to force Phelan to renegotiate for higher compensation, Phelan has him garroted in his own quarters (Black Market). Fisk is succeeded by former engineer Barry Garner as commander of Pegasus (The Captain's Hand).