Complex sentence: Gellibrand performed staff duties during the Gallipoli Campaign, but failed to impress Bridges, and requested a transfer to the 2nd Division after being superseded by Foott.
Split into simpler sentences: Gellibrand performed staff duties during the Gallipoli Campaign, but failed to impress Bridges. Gellibrand requested a transfer to the 2nd Division after being superseded by Foott.