 Rear Admiral McGrigor issued an operational memo to the air units selected for Operation Mascot on 4 July , outlining how the attack would be conducted and providing further orders for the raid eight days later . In accordance with these instructions , the flying squadrons assigned to the three carriers undertook training exercises from their ships and shore bases from 4 July onwards . Intelligence gained from decrypting German radio messages during early July , and photos taken by a RAF aircraft on 12 July , provided further evidence that the battleship was once again fully operational and possibly preparing to put to sea . The airmen were informed on 13 July that they would attack Kaafjord in four days time . 
