On two worlds the great construction plants were humming with activity. Civilian production of all but the barest essentials had been put aside for the duration of the emergency. Space ships were being turned out at top speed, getting their fuel from the wrecks of the invaders' cruisers. Each ship needed only a small amount of the light-metal, for the energy content was tremendous. And those ships had been gigantic.

Already there was a fleet of speedsters and mother ships out there in space, and with every passing hour others left the home planets, always adding to the fighting force that was to engage the attackers deep in space, where no stray ships might filter through to destroy the cities of Earth or Venus. Assembly lines were now turning out ships so rapidly that the training of their operators was the most serious problem. This difficulty had finally been overcome by a very abbreviated training course in the actual manipulation of the controls on the home planets, and subsequent training as the squadrons raced on their outward courses.

It was soon decided that there must be another service beside that of the ordinary ships. One plant was devoted to making huge interstellar liners. These giants, made on Venus, were nearly a quarter of a mile long, and though diminutive in comparison with the giant Nigran ships, they were still decidedly large. Twelve of these could be completed within the next month, it was found; and one was immediately set aside as an officers' headquarters ship. It was recognized that the officers must be within a few hundred thousand miles of the actual engagements, for decisions would have to be made without too much loss of time in the transmission of reports.

The ship must not be brought too near the front lest the officers be endangered and the entire engagement lost for want of the organizing central headquarters. The final solution had been the huge central control ship.

The other large vessels were to be used to carry food and supplies. They were not to enter the engagement, for their huge size would make them as vulnerable to the tiny darting mites of space as the Nigran ships had been to the Interplanetary Patrol. The little ships could not conveniently stock for more than a week of engagement, then drop back to these warehouses of space, and go forward again for action.

Throughout the long wait the officers of the Solarian forces organized their forces to the limit of their ability, planning each move of their attack. Space had been marked off into a great three-dimensional map, and each ship carried a small replica, the planets moving as they did in their orbits. The space between the planets was divided off into definite points in a series of Cartesian co-ordinates, the sun being the origin, and the plane of the elliptic being the X-Y plane.

The OX line was taken pointing toward one of the brightest of the fixed stars that was in the plane of the elliptic. The entire solar system was thus marked off as had been the planets long ages before, into a system of three dimensional latitude and longitude. This was imperative, in order to assure the easy location of the point of first attack, and to permit the entire fleet to come into position there. A scattered guard was to remain free, to avoid any false attacks and a later attack from a point millions of miles distant. Earth and Venus were each equipped with gigantic ray projectors, mighty weapons that could destroy anything, even a body as large as the Moon, at a distance of ten thousand miles. Still, a ship might get through, and with the death ray—what fearful toll might be exacted from a vast city such as Chicago—with its thirty millions! Or Karos, on Venus, with its fifteen and one half millions!

The tension became greater and greater as with each passing day the populace of two worlds awaited the call from the far-flung guard. The main bulk of the fleet had been concentrated in the center of their great spherical shell of ships. They could only wait—and watch—and prepare! Hundreds of miles apart, yet near enough so that no ship except perhaps a one-man craft could pass them undetected; and behind them were ships with delicate apparatus that could detect any foreign body of any size whatever within a hundred thousand miles of them.

The Solar System was prepared to repel boarders from the vast sea of space!