No. 52 Squadron RAF flying Hawker Hinds. This unit was joined on 1 March 1937 by No. 63 Squadron and its Hawker Audaxes. During their time at Upwood, No 52 and 63 Squadrons became training units and took on both Fairey Battle and Avro Anson aircraft. In August and September 1939, the two squadrons were reassigned opening the field up to its new tenant, No. 90 Squadron flying Bristol Blenheims. Second World War With the invasion of Poland on 1 September 1939, Second World War was underway. However No 90 Squadron spent most of its time in air-to-air firing and bombing practice. They were joined in February 1940 by another medium bomber unit, No. 35 Squadron, flying both Blenheims and Ansons. Both Upwood squadrons were not destined to see front-line combat as, on 8 April 1940, they were merged into the new No. 17 Operational Training Unit RAF and tasked with training aircrews. Although the Upwood units were not taking a direct part in the war, they did see some action. On two occasions in 1940 and once in 1942 the airfield was attacked by Luftwaffe aircraft. However, only one person was killed during these raids. On 1 February 1941 a German spy, Josef Jakobs, was captured by farmers after he had parachuted into the area, breaking a leg in the process. He was discovered to have maps of the RAF Upwood area, a code device and almost £500 cash in his possession. Jakobs was sent to London where, after a preliminary interrogation by MI5, he spent several months at Dulwich Hospital. Jakobs was transferred to Camp 020 in April 1941 where he was interrogated by agents of MI5. On August 4 and 5, Jakobs was tried by court-martial at the Duke of York's Headquarters where he was found guilty of treachery. Jakobs was executed by firing squad at the Tower of London on 15 August 1941. Since its opening in 1937, Upwood had seen frequent periods where flying operations had to be curtailed or halted altogether due to the grass airfield being unserviceable. This unserviceability was caused by the levels of rain and general dampness of the area. When No 17 OTU was chosen for transition to Vickers Wellington bombers, it was decided to move the unit from Upwood as the field would never take the pounding from these heavier aircraft. When 17 OTU departed for RAF Silverstone in