The fortress of Calais was of great importance to England as well as to France. With the fortress of Calais, England could easily meddle in continental affairs and easily land a large army in the port of Calais before raiding northern France.

Originally, this is how Henry VIII harassed France. Because Henry VIII's first queen was Princess Catherine of Spain, Henry VIII was very compatible with Spain in the early days. Whenever the French army went south to fight in Italy, England would land their troops at the port of Calais and plunder the northern coast of France. When the French reacted and counterattacked, the English army withdrew into the fortress of Calais in a hurry, and then landed at the port of Calais and returned to England, which made the French very angry.

The French could not take the fortress of Calais and could not control the English Channel. In addition, England chose the timing of its troops, and when they all chose the main French force to go south, there was no way for the French to take England.

But since Henry VIII's daughter, Bloody Mary (Marie I), lost Calais, England could no longer easily attack northern France. After all, the landing of a large army requires a safe landing in the port. The Calais fortress can not only cover the landing of the British army, but also protect the retreating British army from being pursued by the French army, and its function is difficult to replace.

After the French recaptured the fortress of Calais, the northern region was much more stable, and they no longer worried about the English army plundering the northern plains. After that, the English could only raid the ports of France on a small scale, and could not go deep into the interior to sack France......

Edward was not stupid, he also knew the importance of the fortress of Calais. However, because he was not sure of retaking the fortress of Calais from the French, he gave up. Now, with a chance to retake Calais, Edward didn't want to give it up.

However, Edward also had his hesitations:

"Even if the city gate is opened, the 5,000 French troops in the city are not easy to mess with. It is said that there were 500 of France's most elite plate infantrymen in the city. To deal with them, you have to use muskets. However, on a rainy day, it seems that the musket will not be used...... No, the muskets of the North Sea Country can be used on rainy days, Count Marin, do you want to support me? ”

Marlin nodded:

"That's fine, I'll support you with 1000 musketeers. They were each armed with 50 clockwork carbines, enough to deal with the 500 French plate infantry. ”

Edward nodded:

"That's good, in this battle, I plan to send 20,000 troops, and your fourth and fifth legions will send 10,000 troops, how about it?"

Marlin shook his head:

"I can only send 5,000 troops, and I will never admit that those 5,000 are my people. Your Majesty, the minister is different from you, and the minister's Beihai country is on the road. Once the fortress of Calais was lost, the French could not afford to cross the sea to find trouble with England, but they had no problem with trouble with the North Sea State. ”

"So, this time the minister came here and deliberately pretended to be at odds with you, just because I was afraid that the French would know that I was willing to send troops to help you recover the fortress of Calais. If 10,000 people are dispatched, it is easy for the French to see through it. With 5,000 people, it is relatively easy to conceal. After all, most of it is Your Majesty's army. Moreover, after the battle, the minister's soldiers and horses would withdraw overnight, and the French would not be given a chance to inquire about the news......"

"You're so afraid of the French?" Edward's face was speechless.

Marin shook his head and didn't speak. He had already said that the North Sea Kingdom was on land, and the French could not retaliate against the British, and they might be angry with him. Therefore, avoiding suspicion is a must......

In fact, at this time, the strength of the French mainland is not very strong. After all, the main force is Napoli. If Marin is ruthless, he can also deal with those people in mainland France. However, Marin was worried that he would be stabbed in the back by the German princes. Moreover, if France really falls, Spain will emerge and become Marin's mortal enemy. So, Marin would rather keep a low profile now than take the plunge.

In addition, Marin actually hid a killer weapon and didn't tell Edward. Of course, this is just a backup. Only when the sewer gate is unusable will Marlin use the killer weapon......

……

What's the killer feature? Marin actually dug a tunnel in Calais that connected the city to the outside of the city......

It's just that there is something wrong with this tunnel - it is flooded......

In fact, Marin had already sent spies to dig tunnels in Calais. But the French in Calais were very strict, so it was difficult to dig tunnels. The main difficulty was how to avoid the eyes of the French and dispose of the soil excavated during the tunnel.

In order to avoid the eyes of the French, the spies only had to use the carriages entering and leaving the city to spread a layer of dirt on the carriage grounds, and quietly carry the dirt out of the city. Then they dug a well openly, but openly took out a lot of dirt. Moreover, the exit of that tunnel is on the wall of the well......

This method was actually developed by Marin based on the text "The Underground Printing House in Tbilisi" that he had learned in his previous life. After all, no one is willing to go down the well to find some tunnels.

However, in the end, the tunnel was dug and something went terribly wrong - in the part outside the city, an underground river was dug through, and a large amount of water poured into the tunnel......

Then, the tunnel more than 200 meters long was filled with water. Moreover, the exit outside the city was actually at the bottom of a small river......

More than two years of hard work were ruined, and Marin, who learned the news, was so angry that he wanted to kill someone. After blocking the exit hole at the bottom of the creek outside the city with stones, the tunnel was temporarily abandoned.

Until some time ago, Marin had a cylinder and a pump made......

Because of the rubber, making the valve is simple. Whether it's a water valve or an air valve, it's all made easy.

Marlin showed that people made a pump to lay the foundation for the future of making rubber tires. He then asked a blacksmith to help him make a cylinder similar to the liquefied gas tank of later generations. Originally, Marin wanted to use this cylinder to collect liquefied gas for refining gasoline. After all, it's too wasteful to let liquefied gas escape directly into the air.

Unexpectedly, Marin had a whim and used a pump to inflate the cylinder, and then gave birth to the oxygen cylinder commonly used in diving in later generations......

It should be pointed out that the gas cylinders used for diving in later generations were not filled with oxygen at all, but compressed air. Marlin pressed it into the cylinder with a pump, which happened to form the diving cylinder commonly used in diving in later generations......

Then, Marin naturally thought of "inventing" the supporting diving equipment! What diving masks and breathing masks, as well as rubber tubes for ventilation......

The most important thing for these things is that they should be well sealed and not leak. And with rubber, it's not too difficult. After hundreds of failures, a qualified product is made......

……

In this way, the tunnel that had been dug in the first place was useless - as long as someone carried a compressed air cylinder and a diving suit, opened the stone block at the bottom of the river that blocked the hole, and then could dive into the city along the underwater passage. Then, through the well in the city, he went out and into the city......

With hundreds of compressed air cylinders and diving suits, Marin can enter the city through this underwater passage and secretly open the gates......

This underwater secret passage is a bit like the passage from the ancient tomb sect to the outside world in Jin Yong's "The Legend of the Condor Heroes". It's just that in the inside, that passage can only be swam through by people with strong martial arts who hold their breath, otherwise they will almost drown like Li Mochou.

But Marin understands science, and he has vulcanized cooked rubber, so he can calmly build a diving breathing apparatus that allows ordinary people to pass through this long underwater passage......

Of course, this is only an alternative. Only if the plan to use the iron gate of the sewer fails, will this plan be used as a killer weapon to conquer the fortress of Calais......