A special twist was introduced in Harry Turtledove's "Worldwar series" depicting an alternate history in which WWII is disrupted by extraterrestrials invading Earth in 1942, forcing humans to stop fighting each other and unite against this common enemy. Turtledove depicts the tactics and strategy of this new course of the war in great detail, showing how American, British, Soviet and German soldiers and Jewish guerrillas (some of them historical figures) deal with this extraordinary new situation, as well as providing a not unsympathetic detailed point of view of individual invader warriors. In the war situation posited by Turtledove, the invaders have superior arms, but the gap is not too wide for the humans to bridge. For example, the invaders have more advanced tanks, but the German Wehrmacht's tank crews facing them - a major theme in the series - are more skilled and far more experienced.