It's interesting that Hitler was thinking in terms of attacking the Western Allies in 1943. I take it the Germans thought they would be done with Barbarossa by then?
Barbarossa was a war expedient undertaken because of Hitler's mistaken belief that the only reason the British refused to make peace in July 1940 'despite her hopeless situation' was in the hope that the Russians would betray Germany and enter the war. Prior to War Directive No. 18, issued on 31 July 1940, Hitler did not have any serious discussions about an invasion of the Soviet Union from the time he assumed power in 1933, through until the war commenced. In the Hossbach Memorandum, the record of the 5 November 1937 Fuhrer Conference where Hitler spelled out his plans for the coming years, Russia is mentioned in only a single sentence, and that is only to say that their involvement can be deterred by the swiftness of German actions elsewhere and by the threat from Japan. Hitler was
partially correct; the British
were fully aware that there was no way militarily that they could defeat Germany on their own, and that even to have a hope of surviving they needed help - but they were hoping for
American help,
not Russian. (See the War Cabinet report: British Strategy in a Certain Eventuality, 25 May 1940)
In fact, only the month before he issued Directive No. 18, Hitler fully believed that the British
would negotiate and that therefore
the war was over; consequentially he issued orders for the demobilisation of 30 divisions, the first stage to returning Germany to a peacetime footing. On 24 June 1940, Hitler told his inner circle that:
"The war in the West is over. France has been defeated and with England I shall reach an understanding very shortly. There will remain our settling of our accounts with the East. But that is a task that opens global problems, such as the relationship with Japan and the balance of power in the Pacific, problems that we may not be able to tackle perhaps before ten years; perhaps I shall have to leave that to my successor. Now we'll have our hands full, for years, to digest and consolidate what we have achieved in Europe."
Hitler's decision to invade the Soviet Union was prompted by the report that Churchill had sent a personally written letter to Stalin hoping to open discussions between the two nations*. Hitler concluded from that letter that Britain was only holding out in the hope that the Russians would come into the war. He told the Wehrmacht commanders that:
"In the event that invasion does not take place, our efforts must be directed to the elimination of all factors that let England hope for a change in the situation. Britain's hopes lie in Russia and the United States. If Russia drops out of the picture, America too is lost for Britain, because the elimination of Russia would greatly increase Japan's power in the Far East... Russia's destruction must therefore be made part of this struggle."
Hitler's earlier order to demobilise 30 divisions as a consequence had to be reversed, but Hitler was not yet fully settled on the idea of invading Russia; although he never had high hopes of success with the direct attack on Britain, he allowed preparations for Sea Lion to continue just in case it yielded results and the British broke, or failing that, at least asked to negotiate. He also allowed Ribbentrop to continue negotiations with the Soviets to bring them into a direct anti-British alliance (which would have eliminated British hopes in Russia completely), these continued through until November 1940.
*Ironically enough, the report had come from Stalin himself. He'd had no interest in betraying the Germans and ignored Churchill's letter, but he thought that if Hitler somehow got word that Churchill had written a letter without Stalin informing him of it, that would have raised the Fuhrer's suspicions. So Stalin told the Germans about the contents of Churchill's letter, thus setting in motion the chain of events that would lead to the German invasion of the Soviet Union.