What if the Nazis went after the British colonies and protectorates in Africa and the Middle East before going ahead with their main goal, conquering Russia?
Considering that in OTL, Britain had touble holding on to them despite the fact that the Nazis were basically fighting the Soviets and leaving behind a only a skeleton crew for the Western Front, the Nazis conquest of these colonies before invading Russia would be a cakewalk. Especially since the Nazis would have had sympathies among the anti-Semitic Muslim rulers.
They would then have their hands on the precious oil in the region, effectively forcing the British, who depended on the oil, to the table. If this happens, would Operation Barborossa then be a success since the Nazis would only have to fight on one front and with the oil resource in the Middle East in its hands?