The Pirate Planet

A flash of light on Venus!-and at Maricopa Flying Field Lieutenant McGuire and Captain Blake laugh at its possible meaning until the radio's weird call and the sight of a giant ship in the night sky prove their wildest thoughts are facts. "Big as an ocean liner," it hangs in midair, then turns and shoots upward at incredible speed until it disappears entirely, in space!
It is war. Interplanetary war. And on far distant Venus two fighting Earthlings stand up against a whole planet run amuck.
Charles Willard Diffin was an engineer, airplane salesman and writer. He authored hundreds of science fiction stories many for pulp magazines during the 1930s and '40s.