« Second Contact » Harry Turtledove

It is 1963, and Earth is divided among five independent powers (the U.S., the Soviet Union, the Third Reich, Britain, Japan) and the invading alien Lizards. Human adaptations of Lizard technology (including space flight) and the Lizard leaders’ painful experience of fighting humans have led to an armed truce among all the parties. Now, however, the Lizard colony fleet, with 40 million sleep–frozen colonists, arrives to settle what they expect to be a completely subdued world. That the Tosevites (humans) are still holding out is only the first of several surprises to greet them. The nastiest is probably that ginger, merely addictive to Lizard males, brings Lizard females violently into heat — arousing an irresistible mating urge in the males.The Third Reich, meanwhile, under the leadership of Himmler, continues its odious ways; Jews maintain an uneasy peace with the Lizards, who saved them from the Holocaust; the Soviet Union (under Molotov) survives; and the U.S. is building a huge space station.