How after the great wars that had almost seared his life from the Earth's surface, when man's weapons--and his medical science--had wiped out every creature save the indestructible destroyer himself, the machine races had risen from the shreds of technical knowledge hoarded by the scattered groups of survivors and crystallized by their descendants in the rigid mold of tradition. And how that last war had never ended, but had passed into the nature of things in the unending war of the predatory machines against the feeders on sunlight, and of the races of land and air and sea for mastery of their habitats. "But no matter who wins, no man is master; the machine is the ruler, and man is its slave. It is against that we have begun to fight, now, after all the long dark ages...." For one place on all the harried Earth had provided the relative security and permanence needed to keep alive a spark of the ancients' culture. That was aboard the great ships at sea, that had been built and armed to resist every hellish technique of destruction known to the dead age of their building, and were wholly invulnerable to today's weapons. Those were floating cities in truth, with atomic power plants, machine shops, dwellings, hospitals, storehouses, recreation space, libraries--and in the later times, when their first purpose as warships had been almost forgotten, classrooms and laboratories where the knowledge of the past was dredged up from the memories of men and from the books, and even added to in some ways. "We have built up the nucleus of a new civilization on the sea," said Relez solemnly. "Now the time has come for it to take root on the dry land. But first the continents must be pacified. The world must be taken from the warring machines and given back to man. "We possess some of the old ones' weapons, and we could try to use them to enforce our will, as they did. And I think our end would be like theirs. But we have invented some new devices to serve the cause of peace. The anti-ionization field is chief among those. I myself had some share in developing it--my title of 'captain' means leader of a group of scientists, not master of a ship." "Is there no defense against the field?" asked Torcred shrewdly. * * * * * Relez eyed him thoughtfully. "There are ways of avoiding the effect," he admitted, "but they are not likely to occur to these custom-bound people. And once they are liberated from the tyranny of the machine--" "Your method of liberation," said Torcred, "is to reduce everyone to an equal helplessness, and let them fight it out among themselves?" "You might put it that way. I'm afraid there will be some bloodshed. The predatory peoples, naturally, will have the hardest time at first. But--Suppose _you_ tell _me_ what you think will happen, for example, when the terrapins come in contact, under the new conditions, with their old enemies and prey, the trailer people."