Children of the Lens by E.E. Smith

Inch by inch, foot by foot, Kinnison fought his way back along the corpse-littered corridor. Under the ravening force of the attacker's beams his defensive screens flared into pyrotechnic splendor, but they did not go down. Fierce-driven metallic slugs spanged and whanged against the unyielding dureum of his armor, but that, too, held. Dureum is incredibly massive, unbelievably tough, unimaginably hard -- against these qualities and against the thousands of horsepower driving that veritable tank and energizing its screens the zwilniks might just as well have been shining flashlights at him and throwing confetti. His immediate opponents could not touch him, but the Boskonians were bringing up reserves that he didn't like a little bit; mobile projectors with whose energies even his screens could not cope.

He had, however, one great advantage over his enemies. He had the sense of perception; they did not. He could see them, but they could not see him. All he had to do was to keep at least one opaque wall between them until he was securely behind the mobile screens, powered by the stupendous generators of the _Dauntless_, which VanBuskirk and his Valerians were so earnestly urging toward him. If a door was handy in the moment of need, he used it. If not, he went through a wall.