Children of the Lens by E.E. Smith

Thousands of years were to pass before Christopher Kinnison could develop the ability to visualize, from the contemplation of one fact or artifact, the entire Universe to which it belonged. He could not even plan in detail his one-man invasion of Eddore until he could integrate all available data concerning the planet Kalonia into his visualization of the Boskonian Empire. One unknown, Ploor, blurred his picture badly enough; two such completely unknown factors made visualization, even in broad, impossible.

Anyway, he decided, he had one more job to do before he tackled the key planet of the enemy; and now, while he was waiting for the dope on Kalonia, would be the best time to do it. Wherefore he sent out a thought to his mother.