The Defender was the first fighter aircraft to serve with the Krakabloa Air Arm. The need for a fighter arose from the heavy losses being sustained by 'Conveyor' bomber aircraft which were flying unescorted to their targets on the Wright Isles and so the defender was designed to provide fighter cover after a failed earlier attempt to produce a fighter aircraft. There was a great amount of redesign and modification between the first mark of Defender and the last.

The Mk.2b was a vast improvement over previous marks. It featured a redesigned wing and propellor, and the engine was upgraded to give more power. Faster and more manoeuvrable than its predecessors and its opponents, this aircraft did much to prevent bombing raids from 'Spider' aircraft for a significant amount of time and regain the initiative for the KAA.