He was the first ship to communicate with President Sheridan when he arrived at Earth on the Excalibur. At first, he did not believe in the seriousness of the threat and thought the mobilization was just a training exercise. He of course changed his mind when the Drakh arrived with their Death Cloud and their battle fleet.
Behind the scenes
The novelization of "A Call to Arms" spells his name as Yuri Mikhail Denisovitch.