The Snowbank Orbit by Fritz Leiber

When the First Interstellar War erupted, the pioneer fleets of Earth's nations had barely pushed their explorations beyond the orbit of Saturn. Except for the vessels of the International Meteor Guard, spaceflight was still a military enterprise of America, Russia, England and the other mega-powers.

During the first months the advantage lay wholly with the slim black cruisers of the Enemy, who had an antigravity which allowed them to hover near planets without going into orbit; and a frightening degree of control over light itself. Indeed, their principal weapon was a tight beam of visible light, a dense photonic stiletto with an effective range of several Jupiter-diameters in vacuum. They also used visible light, in the green band, for communication as men use radio, sometimes broadcasting it and sometimes beaming it loosely in strange abstract pictures that seemed part of their language. Their gravity-immune ships moved by reaction to photonic jets the tightness of which rendered them invisible except near the sun, where they tended to ionize electronically dirty volumes of space. It was probably this effective invisibility, based on light-control, which allowed them to penetrate the Solar System as deep as Earth's orbit undetected, rather than any power of travel in time or sub-space, as was first assumed. Earthmen could only guess at the physical appearance of the Enemy, since no prisoners were taken on either side.