What Spartans Remain?
Because I went down the Halopedia rabbit hole and I'm an obsessive nut, I've put together a list of all the Spartan-IIs, just to figure out who's alive, who's dead, who's missing, and the numbers which are unaccounted for

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What Spartans Remain?
Because I went down the Halopedia rabbit hole and I'm an obsessive nut, I've put together a list of all the Spartan-IIs, just to figure out who's alive, who's dead, who's missing, and the numbers which are unaccounted for
Happy birthday to Admiral Serin Osman!
Today is her -485th birthday!
Osman had a difficult upbringing: born to single parent and severely neglected. In 2517, she was abducted as part of the Spartan-II program. She was one of the few candidates who were not replaced by a flash clone, presumably because she would not be missed or her disappearance would not be reported.
Osman went through training with the other Spartan-II candidates and was designated as 019, but when it came time for augmentation, she was only able to complete one round before her body began to reject the process. As a result, she was deemed a wash-out and removed from the candidate pool.
ONI took custody of her, rehabilitated her, and prepared her for reassignment. At some point, she was taken under the wing of CINCONI Admiral Parangosky and was groomed as her protégé.
Osman would act as an ONI field agent for several years. By 2553, she had the rank of Captain. Following the end of the war, Osman was selected by Parangosky to participate in covert efforts to disrupt peace between the UEG, the UNSC, and the Swords of Sanghelios, believing that peace was unrealistic and the Sangheili needed to be weakened for Humanity to be safe. She also personally arrested Catherine Halsey, whom she grew to resent deeply over the years.
Because she was taken into ONI training at such a young age, it is difficult to ascertain how much of her beliefs are her own, and how much is just an extension of Parangosky. Upon her retirement, Osman was appointed as CINCONI, ensuring that Parangosky's priorities would be carried out. Like her predecessor, she has an intimidating, conniving nature and reputation. She was given Parangosky's personal AI, Black-Box, as part of her new position.
During the Created conflict, Black-Box coordinated an escort off Earth along with Admiral Hood. They were taken to Rossbach's World, an uncharted, undeveloped planet with a single cabin erected by Black-Box to use as a safe haven. With her, she held a briefcase containing the matrices of all HIGHCOM AIs, including Black-Box, and was left with the decision of whether to destroy them before they could allign with Cortana, attempt to recruit them, or let them choose. She and Hood stayed there for a year, completely isolated and unaware of what was happening in the greater galaxy.
In 2559, Cortana's forces became aware of Rossbach's World and sent a Guardian to the planet. Spartan Gray team was sent to extract them, both because of their individual importance but also for information secretly stored in Black-Box.
Osman reluctantly relinquished Black-Box to the UNSC, having never been able to bring herself to destroy him given their personal history. However, by the time they were rescued, he had already reached his maximum allowable lifespan. Thus, they were both aware that he would be terminated once she surrendered him. After a bitter and tearful farewell, Osman rejoined ONI’s efforts against the many remaining threats against humanity.
In canon (~2560), she is turning 49!