This time, Marlin is more cautious and safety-conscious. In addition to putting gas masks on the soldiers who were tested, longer glass troughs were used. The notch of the glass trough is facing the iron door, but after the aqua regia touches the iron door through the glass trough, it will definitely corrode out the void and then flow down.

Therefore, Marin asked people to throw a bundle of grass under the city gate first. In this way, even if the regia flows to the ground, it will fall on the haystack. Not to mention the corrosion of aqua regia on the haystack, but aqua regia must have been stagnant by the haystack and will not flow everywhere, let alone the feet of the soldiers.

In addition, Marin also changed the experimental soldiers into shoes made of multiple layers of cowhide. In this way, even if the regia water flows to the feet, it will corrode off one or two layers at most. Because, aqua regia corrodes much worse than metals. Just the performance is stained, at most burns out the skin. Therefore, the sole of the multi-layer leather on the ship can protect the foot. Of course, you can't stand in aqua regia for too long to give aqua regia enough time to corrode.

After testing, the soldier in charge of the experiment was indeed successful. It didn't take long for the aqua regia to corrode the iron door into a big hole.

Next, it's time to blow up the door. However, before blowing up the door, the fighters of the demolition team were also seriously afraid of the aqua regia on the ground and did not dare to step forward.

Then, Marin came up with a solution......

He first asked the Demoman to put on a gas mask as well. Then, in front of the Demoman, send a man to sprinkle quicklime in front of the door. Quicklime is a strong alkali, while aqua regia is a strong acid. When the acid and base are neutralized, it is not so dangerous on the ground.

The Demoman then went on, shoving the powder keg into the corroded hole in the iron door......

……

However, after a blast, the blockage behind the iron gate was blown away, but the iron gate was still standing......

Marin looked stunned for a moment, then began to think......

After a while, it dawned on Marin -

"I understand that even if the blocking material behind the iron door is blown up, the iron door is very difficult to blow up. So, what about our corroded deadbolts......"

Then, he began his second attempt. This time, he asked the soldiers to not only pursue a large hole in the iron door, but also to make it corrode the deadbolt.

In this way, when the large hole is corroded, it will be corroded away along with the deadbolt. After the blasting again, although the iron door was not damaged, the door bolt had been corroded, and the debris accumulated behind the door was also blown away. At this time, you can directly let people push open the iron door and enter......

Then, Demolitionist Captain Doni. Ziri proposed a new solution - corroding the door shaft of the iron door. In this way, without the door shaft, the iron door must have collapsed directly......

However, after testing, the effect of corroding the door shaft is not good......

It's not that the door shaft is difficult to corrode, but after the door shaft is corroded, the blasting effect of stuffed into the powder keg is very poor. Because the door shaft is located on the edge of the iron door, it is difficult to blow up the accumulation behind the iron door head-on after stuffing it into the powder keg.

Therefore, it is best to corrode the latch in the middle of the iron door. Because the latch is located in the middle of the iron door, it is more convenient to push the accumulation behind the door front after stuffing it into the powder keg. Bursting on the side of the edge of the door shaft can only blow up a small part of the accumulation.

In this way, the tactics of dealing with the Iron City Gate were thus determined......

However, the height of the gate latch varies from city to city. If you corrode the wrong part, it would be a waste of aqua regia. So, Marin sent spies and sent them to the target cities to investigate on the spot, investigate the height of the latches in those cities, and bring back the results. In this way, the next time you go to attack the city, you can directly corrode accurately according to the data......

……

While Marin was busy experimenting with how to corrode the Iron Gate, a major event also happened in Krakow, the capital of Poland - Queen Anne was about to give birth......

Anne had been married to Zygmunt I for several years and was now 24 years old. It was probably Zygmunt I who reached middle age and had insufficient sperm motility. So, Anne married for the past few years and finally got pregnant.

And at the beginning of September 1512, Anne finally reached her due date......

In order to witness this moment, King Zygmunt I of Poland specially rushed back from the battlefield of the Duchy of Mazovia to witness the birth of his own heir.

……

It should be pointed out that before that, Zygmunt I led an army of 15,000 and was fighting on the front line against the Duchy of Mazovia......

The Duchy of Mazovia is a powerful principality in Poland, with an area of about 33,500 square kilometers, which is larger than the direct territory of the Jagiellonian royal family in Poland.

In terms of strength, the Duchy of Mazovia was in no way weaker than the Jagiellonian royal family. So, in peacetime, the Duchy of Mazovia did not like Sigmunt I at all. Moreover, the capital of the principality of Mazovia was known to later generations - Warsaw......

That's right, Warsaw, the capital of Poland in later generations, was also the place where the Warsaw Pact was concluded, which was on a par with NATO. Now it is the capital of the Duchy of Mazovia.

The Duchy of Mazovia is located in the middle reaches of the Vistula River, mainly plains, and is a very fertile agricultural region in Poland. Moreover, the Vistula River is the most important inland waterway in Poland, and the mere collection of taxes on the Vistula River is huge.

The cause of the war between Zygmunt I and the Duchy of Mazovia was caused by the Duchy of Mazovia's blocking of ships and collecting taxes......

Krakow, the capital of the Kingdom of Poland at this time, was located in the upper valley of the Vistula River. When Anne married Zygmunt I, Marin promised to provide Sigismunt I with at least 10,000 yugram (120,000 acres) of fertilizer each year. Then, help sell the grain produced by Sigismunt I's tens of thousands of yograms.

Because part of the secret estate land of Zygmunt I was near Krakow on the upper reaches of the Vistula. Therefore, whether it was Marin who transported fertilizer to Sigismunt I's southern estates, or Zygmunt I who transported grain from some of the southern estates to Marin's North Sea Kingdom, the main route was through inland shipping on the Vistula River.

It stands to reason that there were several vassal states on the Vistula, and both grain and fertilizer ships were taxed. But Prince Zygmunt was king, and after he came forward to say hello, most of the lords agreed to release Zygmunt I's manure and grain ships duty-free. Only the Duchy of Mazovia, ignoring Sigismunt I's greetings, continued to collect toll taxes as it should.

Zygmunt I was suddenly furious - Lao Tzu is the king of Poland, and he can still be blackmailed by one of your local lords? He then signed a decree in a strong manner, ordering the Duchy of Mazovia not to collect any more taxes on the ships of the Jagiellonian royal family.

Unexpectedly, the Duchy of Mazovia not only did not carry out the order, but also seized several grain ships of Zygmunt I in the name of "tax resistance", and planned to confiscate the grain of these ships.

Zygmunt was insulted, and then he sent a large army to attack the Duchy of Mazovia. Ostensibly, it was to "severely punish" the principality of Mazovia, which did not respect the royal family. In fact, Zygmunt I already had plans to annex the fertile principality of Mazovia......

Before Anne's due date, Zygmunt I had already led a large army into the Duchy of Mazovia. Therefore, even though he heard that the second uncle's Beihai Kingdom was in trouble, he couldn't spare himself to help for the time being.

Because of the lag in the transmission of news, when there was a disturbance on the side of the North Sea State, Zygmunt I had already led a large army to the Duchy of Mazovia, and naturally he was unable to support the North Sea State.

However, upon learning that Anne's due date had arrived, Zygmunt I temporarily left his army behind and hurried back to Krakow......

After a night of nervous waiting, in the wee hours of the morning, a baby's cry finally came from the delivery room - "wow"......

……

Zygmunt I was excited, but at the same time a little nervous. He asked:

"Male or female?"

If the husband of the future generation asks this in the first sentence, the wife is determined to be angry - why don't you ask the old lady first?

But in this era, it is most correct for a king to ask "whether it is a man or a woman". Because it's about the inheritance of a royal family......

"Congratulations, Your Majesty, it's a prince!" The voice of a midwife came from the room.

"Wow, it's a prince! Ahaha, I have an heir! Zygmunt I, who was already 45 years old, jumped with excitement.

And in the room, after hearing that a son was born, Anne was also very happy. However, she was too tired, after all, she tossed all night. So, she quickly fell asleep......

In the afternoon, when Anne woke up again, Zygmunt I was already walking happily around with her son in her arms, and clumsily singing nursery rhymes to coax him.

Seeing Anne wake up, Zygmunt I shook her hand and said:

"Good work, Annie!"

Then Zygmunt I asked:

"What do you think is the child's name? John? Charlie? Louis? ”

Anne laughed out loud:

"Haha, I've heard Brother Marin say before that these names are rotten. Just call these names on the street and a crowd of people will answer you. I don't want my son's name to be so old-fashioned, with so many names! ”

Zygmunt I was suddenly embarrassed, he was an incompetent man......

"And what's your name?"

"How about calling Marin? Marlin is the male name of my mother, Mary. Moreover, my brother is a great hero. My son will also learn from my brother in the future and become a big hero! Anne didn't know that his big hero brother had "had an accident". This is Zygmunt I's deliberate blockade of news in order to prevent the pregnant Anne from being too sad after hearing the bad news and affecting her body and affecting the pregnant child.

Fortunately, however, Zygmunt I did not have too many taboos. Seeing that his wife likes it, and Marin can indeed be called a hero. So, he agreed:

"Okay, my son's name is Marin! My son, the crown prince of Poland and Lithuania, will henceforth be called Marin! ”

Early the next morning, Zygmunt I summoned his courtiers and announced the birth of Prince Marin, who was declared his heir. However, whether Prince Marin can finally become the king of Poland still needs to be confirmed by the Polish House of Nobles. That's what the fucking system of electing a king is. Therefore, Zygmunt I could only claim that Prince Marin was his heir, but could not publicly declare him the crown prince of Poland......

Of course, the Polish nobility could not be elected randomly, only within the Jagiellonian royal family. Otherwise, it's going to be messed up. This is also the difference between Poland and Germany - the election of the German emperor is a random election, and those who have the strength can be elected. The election of the king of Poland is based on blood, and royal blood is preferred. Unless the royal family is no heir, it will be another choice. Generally, the son of a king is a candidate, but if you offend the nobles too hard, it is easy to lose the election. This was also to protect the interests of the nobility and avoid the emergence of kings who hated the nobility......