On 1 June 1938, the squadron was reformed from the renumbered elements of "A" Flight of No. 87 Squadron RAF and placed under the command of Flight Lieutenant D. E. Turner. The squadron was posted to RAF Debden in Essex and commenced training on the Gloster Gladiator (the RAF's last biplane fighter). On 4 September the first Hawker Hurricanes began arriving in numbers. With war looking likely in Europe, No. 85 Squadron received the signal ordering its immediate mobilisation on 23 August 1939, the aircraft making up both "A" and "B" Flights were kept at a state of constant readiness and by 1 September the squadron had completed its preparation for the impending move to France.