Following the attack on Rotterdam, RAF Bomber Command was authorized to attack German targets east of the Rhine on 15 May 1940; the Air Ministry authorized Air Marshal Charles Portal to attack targets in the Ruhr, including oil plants and other civilian industrial targets which aided the German war effort, such as blast furnaces.[97][41] The underlying motive for the attacks was to divert German air forces away from the land front.[98] Churchill explained the rationale of his decision to his French counterparts in a letter dated the 16th: "I have examined today with the War Cabinet and all the experts the request which you made to me last night and this morning for further fighter squadrons. We are all agreed that it is better to draw the enemy on to this Island by striking at his vitals, and thus to aid the common cause."[99] Due to the inadequate British bomb-sights the strikes that followed "had the effect of terror raids on towns and villages."[98] On the night of 15/16 May, 96 bombers crossed the Rhine and attacked targets in Gelsenkirchen. 78 had been assigned oil targets, but only 24 claimed to have accomplished their objective.[100][101][102] On the night of 17/18 May, RAF Bomber Command bombed oil installations in Hamburg and Bremen; the H.E. and 400 incendiaries dropped caused six large, one moderately large and 29 small fires. As a result of the attack, 47 people were killed and 127 were wounded.[103][104] Railway yards at Cologne were attacked on the same night.[104] During May, Essen, Duisburg, Düsseldorf and Hanover were attacked in a similar fashion by Bomber Command. In June, attacks were made on Dortmund, Mannheim, Frankfurt and Bochum.[100] At the time, Bomber Command lacked the necessary navigational and bombing technical background and the accuracy of the bombings during the night attacks was abysmal. Consequently, the bombs were usually scattered over a large area, causing an uproar in Germany. On the night of 7/8 June 1940 a single French Navy Farman F.223 aircraft bombed Berlin, the first Allied attack on the capital.[105] The attack was in retaliation for a German bombing of Paris on 3 June.
Despite the British attacks on German cities, the Luftwaffe did not begin to attack military and economic targets in the UK until six weeks after the campaign in France was concluded.