Britain declared war on Germany at 11am on Sunday 3rd September. Less than an hour later the RAF had reconnaissance aircraft up over the North Sea looking for targets to bomb.
The reason why the RAF was searching the North Sea was that the French had banned the British from attacking targets in Germany. After the heavy damage inflicted on Guernica in the Spanish Civil War, the French were greatly worried that if any German towns were hit by bombers targetting weapons factories, the Germans would retaliate with massive force on civilian areas, and since French cities were closer to Germany than British ones the French expected to get hit hardest. So the only targets allowed to the RAF were those where there was no risk at all of inadvertently hitting civilian areas. That meant military bases in remote areas or ships at sea.
The aircraft used for reconnaissance were Bristol Blenheims as their speed and the height at which they could fly were expected to help them elude enemy fighters and anti-aircraft guns. One Blenheim, piloted by Flying officer McPherson of No.139 Squadron, found a strong force of German naval ships anchored in the Schillig Roads off Wilhelmshaven. Unfortunately although the Blenheim could operate at high altitudes, its radio could not. It had iced up and would not work. By the time McPherson got back to base and reported his find thunderstorms were over the North Sea and no attack was possible.
Next day the reconnaissance aircraft tried again, and again it was McPherson who found worthwhile targets near Wilhelmshaven. There were four destroyers and two larger warships - probably Hitler's much vaunted "pocket battleships". This time the weather remained clear, so Bomber Command sent off a large force to attack the warships. This comprised 14 Blenheims from Nos 107, 110 and 139 Squadrons, 14 Wellingtons from Nos. 9 and 149 Squadrons. Hampdens of No.83 Squadron were on standby, but in the event were not used.
The raid that followed proved to be a fine example of the courage and tenacity of the men of the RAF, and the weakness of their equipment.