Miles Edward O’Brien, played by Colm Meaney, is Chief of Operations in Star Trek: Deep Space Nine. Before DS9, he appeared as a recurring transporter chief in Star Trek: The Next Generation. O’Brien is the only major Star Trek character described as both ethnicallyIrish and born in Ireland.
The character of Miles O’Brien was transplanted from TNG to DS9 at the beginning of the latter show. In the story, Miles O’Brien transfers from the Enterprise-D to Deep Space Nine, in the DS9 premiere episode “Emissary“, to serve as the station’s chief of operations. With the help of Jadzia Dax, he devised a way of moving the station from orbit around Bajor to the site of the newly discovered wormhole, allowing Bajor to take possession. He would later assume an additional role as chief engineer of the USSDefiant, which is assigned to Deep Space Nine in the episode “The Search“.
Here he meets Dr. Julian Bashir, who initially irritates O’Brien (Episode: “The Storyteller“), but the two characters eventually become best friends. In particular, they frequently play darts and fight historical battles in the holosuites.
Miles was reprimanded for violating the Prime Directive when he helped an alien from the Gamma Quadrant referred to as “Tosk”, escape from other aliens who had been hunting him in “Captive Pursuit“.
In 2370, he is arrested by the Cardassians and charged with supplying weapons to the Maquis. The charges were dismissed when it was revealed to be part of a conspiracy to discredit the Federation (Episode: “Tribunal“).
After an accident aboard the station in 2371, O’Brien was temporarily shifted forward in time by a few hours. He died when he deliberately contaminated himself in order to determine the cause of events he had witnessed. He sent his future counterpart back in his place “Visionary“.
Miles was temporarily relieved of duty after a visit to the planet Argratha. O’Brien had been falsely accused of espionage and was given the simulated memory of a 20-year prison sentence. O’Brien became paranoid and emotionally distressed upon his return to the station and attempted suicide “Hard Time“.
In 2373, he has a son, Kirayoshi, delivered by surrogate Kira Nerys in episode “The Begotten“.
At the end of Deep Space Nine, O’Brien and his family depart the station to move back to Earth, where Miles is to serve as an engineering professor at Starfleet Academy. The soundtrack accompanying these moments on screen is to the tune of “The Minstrel Boy“.
DS9, in particular, makes mention and the use of Miles many years of experience within Starfleet as a device to allow the character to play a major part within various storylines and as further justification for his holding what is, essentially a command level position while still being a non commissioned officer. Indeed, it is shown that Miles has as much, if not more command experience then those officers he works with. For instance, during a formal extradition hearing regarding Lt. Commander Worf, he is declared an expert in starship combat due to his experiences and asked to critique Worf’s actions. Additionally, Miles provided Worf with some guidance about commanding and managing others during a crisis. Miles style of command can be classified as generally hands on with an emphasis on “thinking on your feet” when solving problem. Although, Miles is not above asserting his authority when required. All of the above having been said, Miles uses a straight forward and common sense approach towards the issues he faces.