Admiral Leyton served as Chief of Starfleet Operations in 2372, and had served as Captain on starships such as the USS Okinawa with then-Lieutenant Commander Benjamin Sisko, whom he promoted to the position of executive officer. (TLE novel: Catalyst of Sorrows)
After first contact with the Dominion in late 2370, Admiral Leyton assumed a hawkish policy stance, believing war to be inevitable. Leyton was frustrated by what he perceived as the lax and appeasement-minded defense policies of Federation President Jaresh-Inyo of Grazer. Believing it to be necessary for the protection of the Federation, Admiral Leyton used his position to attempt a coup d'etat in 2372; key officers in the Sol system were reassigned and replaced with officers loyal to Leyton, and his agents faked evidence of a cloaked Dominion fleet entering the Alpha Quadrant.
Members of Starfleet Academy's Red Squad were then ordered to sabotage Earth's planetary power network, allowing Leyton to manipulate Jaresh-Inyo into declaring martial law. With Starfleet officers stationed all across the planet, Leyton intended to oust Jaresh-Inyo and the Federation Council from power, setting himself up as military dictator of the Federation. His plan was thwarted when Captain Sisko uncovered evidence of Red Squad's sabotage, and when the USS Defiant, carrying evidence of the cloaked fleet fraud, engaged in a firefight with the USS Lakota, which Leyton had ordered to destroy the Defiant. The Lakota and Defiant later relinquished their battles, leading to the coup's failure and Leyton's imprisonment. (DS9 episodes: "Homefront", "Paradise Lost", SA comic: "Loyalty Test")
Leyton was sentenced to serve five years at the New Zealand Penal Settlement for his crimes. In 2374, Leyton received a visit from Benjamin Sisko following Sisko's role in tricking the Romulan Star Empire into joining the war against the Dominion. (DS9 novel: Hollow Men)
Leyton's manipulating of Jaresh-Inyo into declaring martial law later proved to be a deciding factor in 2372's presidential election. President Jaresh-Inyo was defeated after only one term by Federation Councillor Min Zife of Bolarus, who had also favored a more militant stance against the Dominion in preparation for the coming war. (ST novel: Articles of the Federation)
The RPG The Dominion War Sourcebook: The Fires of Armageddon, published by Last Unicorn Games after they had lost their Star Trek licence, states that Leyton's first name is Robert.
Former Star Trek editor Marco Palmieri had announced tentative plans for a Lost Era novel featuring Leyton and the the Okinawa during the Tzenkethi War. However, there has been no further information about this project since Palmieri left Pocket Books in 2008.