So why store the power? he had asked himself. Why not just have men attach ropes to the short arm and heave down on it directly? For small stones, like those they had roughly chipped into spheres, the new machine, the “pull-thrower” as the Vikings called it, was magnificent.

It threw in a perfectly straight line and could be aimed for direction within a couple of feet. The effect of the missile it hurled was literally pulverizing, turning rock to powder and smashing through shields like paper. As they learned how to shoot the weapon with maximum efficiency, its range steadily increased out to an eighth of a mile. And he was sure, if only they would do as they were told, that he could launch ten rocks while a man counted to a hundred.

But his team had no notion of the catapult as a weapon. To them, it was just a toy. Maybe useful one day against a stockade or a wall. Otherwise, a diversion during the tedium of a winter camp in the Fens, with even the traditional Viking amusements of raiding the surrounding countryside for girls and money severely forbidden.

But these throwers would work against anything, Shef thought. Ships. Armies. How would a drawn-up battle-line fare against a rain of boulders from men well out of bow-shot, each one sure to kill or cripple?

He became aware that a cluster of excited, grinning faces was staring at him. The slaves. Runaways from the North-folk or from the lands of the king of the Mark, drawn to the camp here in the flat, soggy borderland between the streams of Nene and Welland by the astonishing rumor that here their collars would be removed. That food was to be had in return for services. They had been told, though they didn’t believe it yet, that they would not be re-enslaved once their masters moved on.

Each of the ragged figures was clutching one of the ten-pound stones, which they had spent the last day or so chipping into shape with a couple of Thorvin’s least-valued chisels.

“All right,” said Shef. “Take the pegs out, dismantle the machine, take the beams back and wrap them in their tarpaulins.”

The men shuffled and looked at each other. One of them, nudged forward by the rest, spoke haltingly, eyes on the ground.

“We was thinking, master. You being from Emneth and that. And talking like us and all. So …”

“Get on with it.”

“We was wondering, you being one of us and all, if you would let us have a shot.”

“We know how to do it!” cried one of his supporters. “We watched. We ain’t got the beef they got, but we can pull.”