Chapter 4

Outside Londinium

Ky looked over Ursinus’s reports. He’d liked the legate back when he’d been an optio, tasked with keeping Lucilla alive, but he missed Velius’s ability to combine thoroughness with succinctness. In Ursinus’s defense, he hadn’t needed to oversee reports detailing the condition and disposition of several thousands of men when he’d been an optio. Scattered as the reports were, it was clear they had the Carthaginians well hemmed into the city.

With the departure two days before of Velius and three legions, along with over half the surviving Caledonians, most of whom were headed home for planting season, Ky’s forces were down to just one-third of their previous strength. If he’d been the commander inside Londinium and he’d had any strength at all, he would have seen this as his chance to make a breakout.

Even if they were outnumbered, the enemy could have concentrated all of their forces on one or two sections of the Britannians’ lines while Ky’s men had to remain spread around the entire city, which ended up being almost an entire circle, split in half by the river, making reinforcing one part of his army from the other a slow and difficult task.

The Carthaginians had extended the walls far beyond what the Romans had built before abandoning the city and even beyond what the Romans in his original timeline would have built, at least according to Sophus’s records.

The original wall had been on just the northern side of the Thames about three and a half kilometers long. The Carthaginians had added an additional wall on the crooked bend on the south of the Thames, allowing them to have a protected area to load and offload ships. Ky had patrols out to watch for ships coming down the river and archers ready to do as much damage to the resupply boats as possible, but the ones that made the trip at night completely blacked out made it difficult for his men to spot. Ky could have stood there and spotted them, since the dark wasn’t an obstacle for him, but as the commander, he had other places he needed to be.

His men had been somewhat successful, turning back several small barges that had tried to make the run into the protected docks behind the Carthaginian wall. In the long run, it was a terrible position. If Ky had been in charge, he would have moved his soldiers to one of the southern port cities as soon as the invasion force was smashed, allowing for easier resupply.

Still, for now, it also meant Ky’s forces were extremely spread out on both sides of the river, creating a supply headache for Ky as well, since he had to have food and essentials carted well west of the city and around, in order to resupply them.

Thankfully, as long as his supply columns stayed away from the walls of the city and had enough guards to protect them from bandits or opportunistic peasants, they were safe enough. His men had done a good job of scouring the countryside of all Carthaginians, but that only meant his supply lines were more or less secure. If the Carthaginians weren’t going to come out to him, Ky needed to find a way to get his men into the city without getting a huge number of them killed. He and Sophus had gone through the problem multiple times, looking at both the southern and northern sections of the wall, looking at attacks down the river, through the only open section of the wall, and looking at massing their limited siege weapons on one small section to achieve a breakthrough, and none had a high enough chance of success. At least not one that didn’t involve getting a large number of his men killed.

If that was the only way to do this, then Ky would order the attack, but he wanted to exhaust all other options before ordering a direct assault by men with ladders on the city walls. He’d ordered more trebuchets, but it would take time for those to get built and arrive, and he wasn’t sure he’d be able to get enough to actually punch through the thick walls.

There was a cough at the entryway to his tent, causing Ky to turn. Hortensius, looking dusty and tired, stood in the doorway. For a man who spent all his time running the largest part of Rome’s manufacturing, Ky hadn’t seen him actually dirty before this moment.

“You look tired,” Ky said, seeing the lines on the man’s face.

“You look exactly the same, which considering the schedule you keep is infuriating. What I wouldn’t give for your endurance.”

“I don’t think you’d enjoy what it took to have it,” Ky said, flashing back to the surgeries and vomit-inducing medication he’d been subjected to when he’d first been selected to be a pilot.

“Probably not. You sent for me?”

“Yes. Now that the forges are going strong and the new mining operations have started, we can start looking at the next set of ideas and inventions I want to implement.”

“Finally. You keep hinting at these things and I wondered if the day I’d get to learn about them would ever come.”

“Some of this is going to be really extensive and difficult to understand. A lot of it you’re going to have to take on faith until you see the end product.”

“I’ve managed to make everything else you’ve given me work. I’m confident I can handle whatever this is.”

“I am too, or I wouldn’t be giving it to you, but I just wanted to prepare you. This is the key to the future of our military,” Ky said handing a stack of scrolls over. “Everything we do moving forward, at least in the martial arena, is going to rely on this.”

He had been working on these instructions even before the battle with the Carthaginians, since he knew this was the next step after they ended the immediate threat from the south.

“It’s a mixture of some kind. Burned wood, brimstone ... and I don’t know what this last thing is. I don’t understand.”

“I know. These things will seem insignificant and benign separately, but when mixed correctly, they can be devastating. I realized it might be confusing, so I had the men gather a small amount of the items days ago when I asked you to come down here, so I could show you the end result,” Ky said, going to a table on one side of the tent and picking up a small covered clay bowl.

Setting it on the table, Ky removed the equally small lid, revealing a grainy, dark powder.

“This is called gunpowder. When lit on fire, it burns incredibly rapidly, releasing a burst of gas, fire, and heat.”

Ky pulled Hortensius back from the table, lit a small piece of paper, and threw it in the bowl. The moment the paper hit the powder, there was a loud hissing pop and a bright flash that caused Hortensius to jump back, hands going to his eyes.

It was over almost as soon as it happened, causing the factory owner to look around the tent, to the bowl, to Ky, and back to the bowl in confusion and amazement.

“Go ahead,” Ky said at the man’s obvious curiosity.

Hortensius stepped tentatively forward, walking around the table the clay vessel had been sitting on, picking up its shattered pieces and turning them over.

“The powder is gone,” he said in amazement.

“Yes. Burned up in an instant. That was a tiny amount. In large amounts, it can be used to destroy huge areas. In small, tight containers, built with metal strong enough to withstand the destructive power, the force of that explosion can be used to make terrible weapons.”

“This is ... incredible. I’ve never seen anything like this. Such a tiny amount of black sand did ... this. Incredible.”

“Like I said, it is the key to winning this war. It’s how we will make up for the manpower difference we have with the Carthaginians.”

“I am impressed with its ... potential, but I don’t see how something like this can be used as a weapon. Maybe against walls or throwing barrels of this at the enemy.”

“It’s just the first piece of the plan. As impressive as gunpowder is, we don’t use it in isolation. It is part of a larger weapon system that will, I promise, eventually make sense. But we’re going to need a lot of gunpowder to make these weapons work, so we need to set up manufacturing to begin producing it now. I’ve written down instructions on the best ways to store the powder so that it remains dry, which is important for its use and safety. I’ve written down descriptions of how to properly mix the parts together. The end result will look somewhat different than what I had here, more like grains of spice than a powder.”

“I recognize charcoal and brimstone, but I don’t know what this last thing is. The words are, strange.”

“The potassium nitrate. There is no Latin name for it, or at least not current Latin,” Ky said. “For our immediate purposes, I’ve listed the exact location where we can mine small amounts, but these caves are going to be difficult to access, and I’ve added in a lengthy section on how to recognize what you’re looking for. That might provide enough to get the process started, but unfortunately, it isn’t going to be enough for what we need. There is a way to produce it ourselves, but it takes time. Even if you get started as soon as you return to Devnum, it will take a year for any of our efforts to produce the substance, and we’ll have to continually be producing it to feed into our factories. I’ve included all the calculations for a staggered production schedule and the size of the facilities needed.”

Ky waited for Hortensius’s reaction when he read exactly what it would take to produce the substance themselves.

“You want us to collect what?” the manufacturer said when he finally got to that section.

Ky had been aghast himself when he’d found out what they had to do to create the potassium nitrate needed to make gunpowder in a pre-industrial civilization. It involved building what the medieval British would have called nitrate beds, which were prepared by mixing manure with wood ash and straw into a large compost pile. The heap was then covered from the rain and regularly moistened with urine, usually from horses because of the quantity needed. After a year, they could remove the soluble calcium nitrate, which could then be mixed with potash, which was derived from wood or plant ash, that they would also have to begin producing right away.

He could imagine the complaints of anyone who might have to work on the nitrate beds, since the smell was going to be something unbelievable, but it was what they needed to do if this was going to work. There was also an alternative Swiss method that was more passive, involving creating sandpits underneath stables, which would have a constant supply of urine from the horses above. The time frame on that one was the same and would help to add to their total output, but there weren’t enough stables in either Rome or Caledonia to produce what they needed, and it would cause disruptions when the stables had to get dug out every year and reset, so it wasn’t a replacement for the larger production nitrate beds.