Saru left the USS Discovery in 3189 to help Su'Kal adjust to life on Kaminar, passing command to Michael Burnham. The following year, Saru returned to the Discovery to serve as Burnham's first officer during the Dark Matter Anomaly crisis, before resigning from Starfleet in 3191 to become a Federation Ambassador, at which point Commander Rayner succeeded him as the Discovery's executive officer.