Pattern for Conquest by George O. Smith (1949)
Science fiction writer George O. (Oliver) Smith should not confused with science fiction writer George H. (Henry) Smith, or even George H. (Hudson) Smith, who happens to be the same George H. Smith. George O. (1911-1981) was an electronics engineer whose science fiction stories were a popular mainstay of John W. Campbell's Astounding Science Fiction in the 1940s, beginning with "QRM -- Interplanetary" (October 1942), the first of Smith's "Venus Equiilateral" series.
Smith was never a literary stylist. His stories clunked along and mainly focused on technical engineering problems of the future. His characters were made of cardboard. But he had a certain something that helped transform the E. E. Smith/Edmond Hamilton style of world-wrecker super-science to a more palatable Golden Age model. One of Smith's specialties was the alien invasion story, as with Pattern for Conquest, where mankind, despite overwhelming odds, just plain outsmarts the aliens because of human superior nature. Campbell loved this approach. Also in Pattern for Conquest there is a bit of extra sensory perception, which augers a major Campbell theme for his magazine over the next decade. George O. Smith was in the mold of science fiction writer that Campbell fancied and published. That is until 1949, when Campbell's wife left him and married Smith. Smith continued in the science fiction field for a decade, publishing novels and contributing to other SF magazines but much of his better work was behind him.
The Loard-vogh is a race that has a 20,000-year plan for conquest of the entire galaxy. Already they have conquered a quarter of the galaxy, with the outer edges of their territory many light years from Earth. They are aware of Earth, calling it "The Planet of Terror," and their plan calls for its conquest in two thousand years. Our solar system happens to be the center of rapid mutation activity due to the effects of an explosion of an anti-matter star millennia ago. This mutation allowed for the rapid growth of bacterial, fungal, insect, and animal life -- something that proves rapidly fatal to the Loard-vogh upon contact.
The spanner in their plan lies with ace pilots and bitter rivals in the Solar Guard Stellor Downing and Clifford Lane, one from Mars and one from Venus. Smith tries to portray the two fueled by hatred of each other, but they basically come off as blowhards who deep, deep down really respect one another. Both are enamored with lovely Patricia Kennebec, the daughter of the nominal head of the Solar Combine. Patricia likes both men but refuses to decide between the two, perhaps in part because of Earthman Billy Thompson, who has been assigned to keep Downing and Lane from killing each other. Not quite halfway through the book, Thompson declares his love for Patricia.
Two aliens from Tlembo, Toralen Ke and Holung Lu, are sent to tell the Solar guard that the Luard-vogh have covered this area of space with mental suppressors which have prevented humans from achieving their true mental potential. Downing, Lane, and Thompson are sent to destroy the suppressors. This brings them into an area controlled by a cat-like race of Sscantoo I, who have a natural antipathy toward Earthmen. Lane and Downing managed to take one of the Cat-men's weapons, improve upon it, and use it to show the Cat-men their superiority. The Cat-men then allow them to enter their territory and destroy the suppressor.
With the destruction of the suppressor, Downing and Lane "merge" their minds while all other humans begin to gain additional mental powers. The Luard-vogh, fearful of Earth's new power, decide to attack Earth immediately, contravening their 20,000 year plan. With a quarter of the galaxy to draw their army from, the Luard-vogh outnumbers humanity by a factor of millions to one. No matter how Earth defends itself, the sheer number of the enemy guarantees humanity's defeat.
Earth puts up a plucky defense, but they are overwhelmed. Downing, Land, Thompson, Patricia, and Kennebec formally cede to the Luand-vogh. Earth has been conquered.
But just because you are conquered does not mean that you are conquered. The Earthmen have an ace up their sleeve. But what is it, and how can it possibly work?
If you are looking for good, old-fashioned space opera, loaded with super-weapons and cagey humans battling against impossible odds, then this might be for you. A touch of the Campbellian-era, Golden Age SF, can be a welcome and fast-paced evening's pleasure.