On Thurs. 21 Dec 1939 The British RAF Bomber Command issued Operational.....

The British RAF Bomber Command issued Operational Instruction 21, which in part noted the following that reflected the reluctance to end daylight bombing missions despite of the heavy losses sustained thus far: "With the intention of combining useful training and operations, sweeps will continue to be carried out.... If enemy aircraft are encountered, gunners will be able to practise shooting at real targets instead of drogues."

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