"They'd be right," Valens said.
Ziani smiled. "I borrowed a book from your library," he said, "I hope you don't mind. It was called The Art of War or something like that; actually, I think there was a mirror in the title. All the books in your library are called the mirror of something or other. I suppose it's a convention. Anyway, not important. The book said, always attack your enemy's strengths and invite him to attack your weaknesses. I reckoned that sounded pretty stupid until I thought about it. Really, it's just simple common sense. He won't expect you to attack where he's strong, so you attack on your terms. Likewise, if you know where he's going to attack you, because you've drawn him into it, you can be ready for him, with a few surprises. Now I come to think of it, that's how the Ducas defended Civitas Eremiae."
The name made Valens look up. "Really?" he said.
"Absolutely. Their strength was their artillery; we attacked their artillery with ours. Our weakness was being pinned down in one place, where they could use their machines against us; we let them come right up to the city, exactly what they wanted to do. I still believe we'd have beaten them if someone hadn't betrayed us. We'd beaten them where they were strong, you see; we'd let them do exactly what they wanted, and then turned round and slaughtered them."
Valens looked at him for a moment. "You know," he said, "I'm sure I must have read that book, but obviously I didn't get nearly as much out of it as you did. What's your idea?"
Ziani straightened his face until it was completely at rest. "What they'll want to do is attack your wagons. I say, let them. Don't be obvious about it, of course. Send out your cavalry, have them do everything they can to keep my people away from the wagons. But expect them to fail."
Valens breathed out slowly through his nose. "With you so far," he said. "Then what?"
Ziani was getting visibly more animated; Valens could have sworn he was swelling, like a bullfrog. "Ask yourself: if my people were in your position, what would they do? Facing the danger of being engaged out in the open by enemy cavalry?"
"I imagine they'd dream up some ingenious machine or other."
"Exactly. Which is what I've done." Ziani was smiling, pleased with himself. "Not machines as such, because anything too complex would take too long to build, and we haven't got enough plant and machinery, or enough skilled people. No, what I had in mind was this." He reached in his pocket. "Here're some sketches that ought to give you the general idea. Of course they aren't to scale or anything."
Valens frowned, and looked at them. "Carts," he said.
"Ordinary carts, yes. That's an important point, because of the time pressure. We need to be able to modify what we've already got, rather than building from scratch."
"Carts with…" Valens paused, looking at the sketches. "This is all a bit far-fetched, isn't it?"
The flicker of annoyance on Ziani's face came and went very quickly. "I don't think so," he said. "What do you do if you want to protect a man from weapons? You put him in armor. Sixteen-gauge wrought-iron sheet; that's about a sixteenth of an inch. You know what level of protection you can expect from it, that's what your helmet and your breastplate and all that are made out of. It'll turn arrows at anything but short range, it'll stop cuts from swords and axes. It's not exactly light, but when you're wearing your armor it's not so heavy you can't move almost as easily as you can without it. Look, we can't carry stone ramparts around with us, or palisades of tree trunks; what we can do is use the wagons themselves as walls. Each wagon has an iron sheet bolted to one side; half of them on the left, the other half on the right. Think of it as each wagon carrying a shield. When the enemy attacks, they do what infantry do: line up, form a shield wall. Instant fortifications. Your cavalry opponents lose all their advantages of mobility and impetus; suddenly they're reduced to being foot soldiers trying to storm a fortress, except they haven't got any siege equipment-no battering rams or scaling ladders or pavises. They can run up and try and climb over, if they're keen enough, but I don't suppose they'll be stupid enough to try it twice. Then, once you've driven them off, you span the horses in again and carry on with your journey as though nothing had happened."
Valens sat and stared at the sketches for a long time. "We're talking about every cart in the duchy," he said at last. "There's not enough sheet iron in the whole world."
Ziani laughed. "Please," he said, "trust me to understand about material procurement. I used to run a factory, remember. That's the real beauty of the whole scheme. Sheet iron is just iron you heat up and bash until it's spread out flat and thin. You don't need trained smiths or engineers, just a lot of strong men with hammers."
"The miners," Valens murmured.
"Strong men used to hammering." Ziani nodded. "And badly in need of something to do. As for iron; well, even simple rustic folk like yourselves use iron for practically everything. You build a dozen big furnaces, say-bricks and clay, nothing complex or time-consuming-and you cook up all the iron tools and furniture and fittings and stuff you don't actually need to take with you on the journey-all the things you were planning on abandoning for the Mezentines to loot, basically; you melt it and pour it into great big puddles, what we call blooms, and then your ex-miners and your soldiers and anybody who can swing a hammer bashes it out into sheets. I'll need a few competent men to cut the sheets and fit them, of course, but that's about it as far as skilled tradesmen go. As for how long it'll take; that'll depend on how many people we can get on it."
Valens said nothing for a long time. "Fuel," he said at last. "You'll need a hell of a lot of coal or charcoal or whatever it is you use."
"All of which you've got," Ziani pointed out, with more than a touch of smugness. "Stockpiled, at the mines. I've taken the liberty of having an inventory made of the supplies you've got available. I think there'll be plenty. Even if the whole idea is a complete failure, at the very least that's one more resource the Mezentines won't be able to load up and take home with them."
That made Valens smile. "Business thinking," he said.
"I'm a Mezentine," Ziani replied. "Cost out everything before you start, know where your supplies are coming from so you aren't taken short halfway through the job, and try not to waste anything. Oddly enough, there's nothing about that sort of thing in your art-of-war book. Maybe that's because you really do think of it as an art, rather than a trade; you expect it to be financed by wealthy amateur patrons, instead of running to a budget."
Valens laughed. As he did so, he realized that the man he was facing was essentially a stranger, someone he hadn't talked to before. Maybe, he thought, it's simply the confidence of an expert in his element; but that wasn't all of it, by any means. The other thing the Mezentines were famous for, he remembered: they were reckoned to be born salesmen.
"All right," he said. "We'll give it a go. Now, you see, I've been learning from you as well. Build me some prototypes, so I can see, for myself if any of this'll work. Build me a shielded wagon, and a scrap-iron furnace. If I give you full cooperation, how long will you need?"
Ziani took a deep breath, as if this was the moment he hadn't been looking forward to. "I'll need to build the furnace in order to make the material for the wagon," he said. "Ten days?"
"You're serious? Ten days?"
"We don't have much time before the evacuation, you said," Ziani replied. "While I'm making these prototypes, I can be training the men who'll be my foremen once we're doing it for real. Yes, ten days."
"Fine," Valens said, frowning. "Ten days. You'll be wanting to start right away, so don't let me keep you. I'll have Carausius write you a general commission; that'll authorize you to make all the requisitions you want, men and supplies. Good luck."