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Commander Barry Garner is the third commanding officer of Pegasus, appointed by Admiral William Adama after the deaths of Admiral Helena Cain and Commander Jack Fisk. Before his promotion, he was the ship's chief engineer.
As commander, Garner does not inspire great confidence and runs the ship like a martinet. Kara Thrace considers him "paranoid and barely competent" (The Captain's Hand), an opinion shared by Kendra Shaw (Razor). Garner holds a similar contempt for both women: he orders Thrace's transfer back to Galactica (The Captain's Hand), and reassigns Shaw to mess duty (Razor).
Garner's rash judgment and lack of experience jeopardizes Pegasus when he disobeys Admiral Adama's orders and takes the battlestar into the binary stellar cloud to recover the missing crews instead of an advance recon of Raptors as instructed.
As Adama suspects, three Cylon basestars ambush Pegasus and damage her FTL. Garner momentarily freezes under the pressure, then decides that he needs to lead the repair team personally, handing the CIC over to Major Lee Adama. Garner enters a compartment which is venting air into space, seals the hatch behind him and finds the coolant leak disabling the FTL drive. Meanwhile, Major Adama's tactics severely damage one of the basestars and throw the others into disarry, buying Garner time to fix the leak. Garner's repair brings Pegasus's FTL back into operation and the battlestar escapes the lop-sided battle. However, Garner succumbs to hypoxia in the compartment and dies.
After the battle, the events surrounding Garner's death are reviewed by both Adamas. Reports were also filed by both Major Adama and Thrace. Major Adama understands that Garner's failure was in treating people as he would a machine, whereas Thrace's assessment of him is considerably harsher (The Captain's Hand).