Fifty Days to Doom

The galaxy is at war, a war between the oxygen-breathing Terran Federation of worlds and the Ginzoes, chlorine-breathing aliens. Neither side dare attack the others'' habitable worlds for fear of reprisals: the war has become a matter of spaceships firing on each other as they emerge from hyperspace.
An Earth ship is captured in battle by the Ginzoes, and its surviving crew learn that the aliens ha...