After nearly a week of assembly and testing, Roland and Anna together completed the development of the bomb contact fuse.

Compared to the fuse of a cannon shell, it doesn't need to withstand high temperatures and pressures, nor the high-G overload upon firing, so the structure is exceptionally simple. But even with such a thing consisting of a firing pin and a spring, the two tested it many times before succeeding.

The main problem was that no one knew how much force the spring needed to prevent accidental firing when dropped accidentally, while also ensuring that the firing pin could reliably trigger the primer when normally thrown.

He and Anna could only test it little by little by changing the thickness and hardness of the spring.

Fortunately, the latter and Lucia had done a lot of preliminary work on weekdays, so Roland had more and more high-quality materials available. The one that finally passed the test was 1365 alloy steel, which has high hardness and low toughness, so even if the bomb fell from a height of one meter, it would not be compressed to the bottom.

Once the appropriate spring was selected, the rest came naturally. Even if Roland had never seen the actual appearance of a fuse, he could design one himself based on its working principle.

It was definitely backward, but it was sufficient for the clumsy and bulky aerial bomb.

The completed contact fuse is like a cylinder, twelve centimeters long and about five centimeters in diameter, with threads at the bottom, which can be screwed into the opening at the top of the bomb.

Its interior is a downwardly convex groove, and the firing pin is similarly shaped, able to fit perfectly into the groove. In the normal state, the upper part of it is pushed against the slot by a spring, and the firing pin falls into the groove, exactly a finger's distance from the primer. For safety's sake, Roland also opened a hole in the head of the firing pin and fixed it to the shell with a cotter pin. The iron rod must be pulled out before the bomb is dropped so that the firing pin can move up and down.

The simulated drop test was conducted on a sunny afternoon.

Since this bomb weighed nearly five Nightingales after being filled with sand and black huoyào, Roland did not board the hot air balloon, but watched with a telescope from three hundred meters away from the drop site.

In addition to him, Iron Axe, the commander of the First Army, and Carter Lannis, the Chief Knight, also attended the test drop.

"You plan to throw a giant package into the palace using a hot air balloon?" After listening to Roland's battle plan, Carter couldn't believe his ears. Launching an attack from an altitude of two thousand meters, ignoring the city walls and defensive forces, completely subverted his previous combat concepts—of course, he had been subverted many times during this year in Border Town.

"As long as it's controlled properly, it's not impossible to achieve," Roland nodded. "Tifice is forcibly conscripting new militia teams. If we can't stop him, the Western Territory will inevitably be attacked by the kèyào army again. Even if we win, it won't bring us any benefit."

The secret letter sent by Tassa indicated that Tifice still wanted to use the same old trick to consume his strength. He wondered if the envoy team sent by Barov could attract more people to Border Town before the other party did.

"If you could really drop the Fury of Heaven on Tifice's head, he would definitely be terrified!" Iron Axe said excitedly. "It's simply an irresistible divine punishment!"

"Hopefully," Roland smiled.

Although Tassa mentioned in the letter that Tifice might have figured out the pèifang of black huoyào and opened workshops in the inner city, trying to produce this dangerous substance in large quantities, he considered it again and again and still chose the palace as the target.

The reason is simple: because the palace is conspicuous enough.

Looking down from a height of two thousand meters, even the most magnificent city in Graycastle is only the size of half a palm, so the landing point must be determined in advance when dropping the bomb. The palace is in the center of the inner city, surrounded by red-tiled walls, and the top of the palace is paved with pure white stone slabs, which looks particularly conspicuous during the fall, making it almost impossible to mistake the target.

But workshops are different.

He didn't have a floor plan of the Royal City, and no one on the ground was guiding him. It was difficult to describe the location of the target clearly with words alone. In addition, the workshop itself was not large. Once the bomb landed off target and fell into a residential building,

this plan would be counterproductive.

Suddenly, a white shadow plummeted to the ground, causing a plume of smoke to rise in the testing ground, followed by a dull thud.

"It seems the bomb has landed," Roland put away the telescope. "Let's go see the results."

After a week of training, Lightning's bombing skills had improved significantly. The aerial bomb landed less than five meters from the center of the target. The entire body of the bomb was embedded in the mud, and the outer shell was greatly deformed by the impact.

When the Longsong landed, Anna used Blackfire to cut open the bomb. Everyone saw that the soil near the fuse had turned into a scorched black mass—this proved that the high-temperature gas from the primer ignited the black huoyào scattered on the surface of the soil, and the fuse itself was working normally. If the inside of the bomb was filled with nitrated starch, it could easily create a deep pit four to six meters deep and kill unprotected personnel within a fifty-meter radius.

Now that the aerial bomb had been developed, the next step was to arrange the battle plan.

Roland glanced at everyone in turn and slowly opened his mouth, "The surprise attack on the Royal City is scheduled for next Monday. First, Iron Axe, you will lead a fifty-man musket team to escort the witches to the outskirts of Silverlight City. There is a mountainous area there that can shield the view, which is suitable for setting up a camp and launching balloons."

"Yes, Your Highness!" Iron Axe responded.

"Aren't we flying directly from Border Town?" Wendy asked.

"No, that's too far," Roland shook his head. It would take at least a week to travel from the Western Territory to the Royal City. Even if the Longsong flew directly, it would take about three days, and six days including the return trip. The basket can only carry two people after the throwing rack is added. Nightingale cannot accompany them, and none of the four witches except Anna have combat capabilities. It is too risky to spend six nights in the wild, and he really cannot rest assured. "If you depart from Silverlight City, it will only take you one day to complete the bombing and return before sunset."

"Next are the witches. The personnel for this mission are Anna, Wendy, Lightning, Macy, Nightingale, and Sylvie. The latter two are responsible for monitoring the surrounding situation of the camp. The attack process will be carried out by the first four according to the training methods, especially Lightning," he looked at the little girl, "Whether it succeeds or not depends on you."

"Leave it to me." The latter patted her chest.

"Then the last thing I want to say is, be careful," Roland said word by word, "I'll be waiting for you to come back in Border Town."

Four days later, the first bomb, Dongfeng-1, was loaded onto a carriage and, under the escort of the First Army, boarded a cargo ship bound for Silverlight City.