A série que você está pensando é chamada de " Worldwar " por Harry Turtledove.
The premise of the series is an alien invasion of Earth in the middle of World War II. The military invasion begins on or around May 30, 1942, but the aliens, who call themselves the Race, reached Earth orbit in December 1941. Presumably, six months were spent making preparations for the attack.
Although the Race, a reptilian species, has the advantage of superior technology, their last information on humans was collected by a robotic probe during the 12th century. Their technology is only marginally ahead of 21st century Earth technology, and much of their equipment relies on basic principles still in use.
Os 4 livros da série são:
- Worldwar: no balanço
- Worldwar: Inclinando o saldo
- Worldwar: perturbando o equilíbrio
- Worldwar: atacando o equilíbrio