Triplanetary was first serialized in Amazing Stories in 1934. After the Lensman series became popular, Smith took his Triplanetary story and turned it into the first of the Lensman series, using it as a prequel to give the back story for the protaganists in the Lensmen series. He added six new chapters, doubling it in size and it's really a different book from the serialized novel, being published 14 years after the first. It was put into Gutenberg just last year.
Written in two parts, Triplanetary introduces the concept of two warring alien races: the Arisians and the Eddorians, whose battles on Earth are unknown to the human race, and in fact the humans are unaware that the Arisians have been secretly and selectively breeding the humans to use as weapons for these battles. From the time of Rome to World War II, the author takes the listener on a lightning-fast journey through Earth's history as the warzone for aliens.
From the atomic age in Atlantis to a world remote in space and time, two incredible ancient races, the Arisians and the Eddorians, are in the midst of an interstellar war - with Earth as the prize.
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