Due to the existence of the large estuary of the Tejo River, and the French army on the southern front (Desay Army) had controlled the river channel in the lower reaches of the Tejo River, General Cole, Lieutenant Colonel Bomé and others clearly realized that the Alhandra Fortress had become the weakest link in the second chain defense line (Torish Vedras Line). As a last resort, the British could only take the initiative to change, and they retreated the front line on the bank of the river to the town of Sheila five kilometers away. However, under the seemingly majestic and sturdy Fortress, no one seemed to know about the fatal hidden dangers that existed under the surface of the seemingly majestic and sturdy Fortress, whether it was the defense of the British or the local Portuguese.

More than 600 years ago, the Mowahid Dynasty tried to stop the then Prince of Portugal, the conquerors Alfonso I, from Lisbon to the north and captured Santalon, the important town in the middle of the Tejo River. Therefore, the Moors also built a large number of fortifications along the central Portugal mountains, and the Fortress of Buselas was also being built. The Christians who were driven out of their homes by the Moors and were forced to participate in the construction of the fortifications of Buselas under the whip of the supervisors. A craftsman leader gathered the people together and began to build a secret tunnel under the fortifications of the fortifications, preparing to cooperate with Alfonso I's army to seize the city.

However, when the secret passage was about to be built to the foundation of the Fortress of Busselas, news came from behind that the sudden fall of Santalon was heard. It was the unexpected death of the Portuguese military commander sent by the Muwashid dynasty, which led to the chaos of the defenders. The Moors were defeated without a fight, and finally handed over the city of Santalon, together with the Fortress of Busselas, to the conqueror, Alfonso I's army.

As a result, the Buselas Fortress and the narrow and long secret passages under the fortress became useless. It was not until the 21st century that a news documentary filmed by the British BBC revealed the extraordinary feats of the determined Christians back then.

By chance, the travelers of the previous life also watched this historical documentary and learned about this secret path that was buried in the long river of history. Before entering Evora, Desai ordered the agents deployed by the Military Intelligence Bureau in Portugal to secretly explore the authenticity of the secret passage below the Fortress of Busselas. After conquering Clisbon, the Military Intelligence Bureau finally confirmed that they had explored the entrance of the secret passage. What is even more gratifying is that due to the long time, neither the local Portuguese nor the British defenders stationed in the fortress were aware of the existence of this secret passage.

In addition, the Military Intelligence Agency agents also reported that the end of the secret passage was at least 50 to 60 meters away from the Busselas Fortress above, so the engineers needed to continue digging upwards. However, this was true. When Wellington ordered the rebuilding of Busselas Fortress, British engineers and Portuguese workers did not discover the major safety hazards buried under the fortress.

In early October, when Desai commanded his more than 20,000 troops to advance north, the Fortress of Bussels established an important breakthrough in conquering the Wellington Line. The troops that took on this main responsibility were Colonel Ultrasle's Engineer Regiment. Of course, there were the First Infantry Division, part of the Artillery Regiment, and two light cavalry regiments temporarily commanded by General Deerney.

The first division's primary task is to cut off the communication and liaison systems between Mafura Fortress, Montachik Fortress, Buselas Fortress, Alhandra Fortress and Sheila Command on the tens of kilometers of coalition defense line; then, he tempted the defenders of various fortresses to take the initiative and then encircle and annihilate them; when the situation came naturally, he cooperated with the engineering regiment to take down the Buselas Fortress.

In the first few days of the battle, everything was very tense. Wellington set up several fortresses on the second line of defense and became information islands, almost completely losing communication with General Cole (Hila Town). In addition, General Mickey Fuli, the commander of the Fortress fortress, the risky attack caused the loss of one-third of the fortress's troops near a mountain, and he did not dare to walk out of the fortress again. This greatly facilitated the secret operation of the Engineer Regiment to rebuild the tunnel.

When Lieutenant Jacques arrived at the station of the Engineer Regiment, he had traveled five or six secret posts in a row. On the last post, soldiers from a combat engineer battalion responsible for the guard duty here directly refused to enter the intelligence officer. After Colonel Altsl, who was familiar with the situation, sent his adjutant to rescue the conscientious sentry allowed Lieutenant Jacques to continue his passage.

The command post of the Engineer Regiment was set two hundred meters away from the entrance of the secret passage. A large forest of shrubs surrounded by a tall and long fence wall seriously blocked the intelligence officer's exploration. Through the gaps between the fence walls and leaves with the flashing light and shadow, he could only see some blurred figures swaying back and forth. When Jacques stood in place and tried his best to look up at the top of the mountain, the scene in front of him was also blocked by steep mountains, rugged rocks, and dense short jungles, and could not see the enemy's traces of the prismatic fortress on the top of the mountain. In addition, the strong wind of the Wusha Stream also blocked the various noises of the top of the mountain and the foot of the mountain, and the enemy and us.

"Lieutenant Jacques, the Fortress of Buselas is at least 1 kilometer above our heads. From here, we cannot see the British, and the British do not know our existence! Of course, even though the British discovered it now, it was too late. They had lost the confidence to leave the fortress and took the initiative to attack out, and they lacked mobile forces." Colonel Ottersle, who came out of the temporary command post, came forward and explained to Lieutenant Jacques in front of them.

The commander of the engineer corps introduced the terrain and enemy situation to the intelligence officer around the marshal in detail. He pointed to a large trench not far away and said: "The head of this outer trench extends to the fortress base. We are in the low-lying area below the fortress, the protruding mountains and rocks above our heads, and the obstacles of large bushes, forming shade that the enemy cannot observe. It has to be said that hundreds of years ago, the Portuguese craftsmen who chose to build underground secret passages here were very smart.

They chose a natural cave as the entrance to the tunnel, digging upwards along the weathered gravel or sedimentary rock eroded by water flow, almost 950 meters. In order to fully ensure the oxygen supply inside the tunnel, they drilled five vents into the tunnel on the hillside, but they were not discovered by nearby Moorish supervisors. In addition, Portuguese craftsmen and their assistants, in order to prevent the weathered gravel and loose soil in the tunnel, caused internal landslides, these people used a large amount of logs and special clay to successfully support both sides and top of the tunnel, and lay the steps to climb upwards. If your Military Intelligence Bureau had not tried his best to find this secret location, even in two hundred years, no one would have noticed the existence of the tunnel."

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Note: Don't doubt that the term oxygen and the understanding of oxygen characteristics have appeared in France for 35 years. And its discoverer is one of the founders of modern chemistry, a member of the Royal Academy of Sciences of the French. Unfortunately, due to the special identity of another tax depositor, Lavoisier eventually died in Paris on the guillotine of the French Revolution-erament.

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Lieutenant Jacques smiled but said nothing as an intelligence officer. As an intelligence officer, he naturally knew who the credit was, but he did not intend to let more people know. After the commander of the engineering regiment finished speaking, the intelligence officer conveyed Marshal Desay's inquiry.

Colonel Otsle frowned and then admitted: "Indeed, we encountered a big trouble yesterday. When the engineers followed the footsteps of Portuguese craftsmen and continued to dig upwards to a position only 7 or 8 meters below the fortress, a large piece of hard granite blocked the way of the tunnel. If they continue to dig, the sound of violently hitting the rocks would inevitably alarm the fortress defenders; if gunpowder was buried here and the final blast was carried out, the effect would definitely be poor, and it would be difficult to completely destroy the bastion above the tunnel. So this morning, I ordered the engineers in the tunnel to dig in a roundabout way to the left and right sides, hoping to avoid this large area of ​​hard granite."

The engineers encountered more than these problems. As the tunnel extended forward, the humidity in the tunnel increased, the operators sweated a lot, and the air in the tunnel became quite turbid. Although the vents dug by the Portuguese hundreds of years ago were still well preserved, 960 meters away, that is, at the end of the ground vent, the oxygen in the tunnel became thinner and thinner, and the situation was getting worse and worse.

Because the air in the tunnel was particularly thin, the engineers involved in the excavation of the tunnel had difficulty breathing, and even the candlelight used for lighting on the walls on both sides of the tunnel became darker and darker until it was extinguished. Starting today, the engineers responsible for excavating the tunnel were generally dizzy, nausea, and vomiting, and people continued to faint on the ground. Two engineers even died of the line due to ineffective rescue.

After learning about the above situation, Colonel Otsle and several civil engineers discussed urgently, he immediately ordered: every time you enter the hole, dig for 30 minutes, the engineers must take turns to get out of the hole and breathe fresh air, otherwise they will faint in the hole. However, this will seriously affect the exploration and excavation speed of the tunnel.

Despite learning about the various difficulties faced by the Engineer Regiment, Lieutenant Jacques expressed the last order of the Supreme Commander, saying: "The Marshal asked to detonate at dawn tomorrow. It is necessary to unplug the Fortress of Buselas before noon to open the right wing passage to the Sheila line for the main force of the First Division and the Artillery Regiment. Sorry, Colonel, the attack order has been issued and can no longer be changed!"

Colonel Ultrasl hesitated, and he knew that there was another last resort: if the underground blasting was not successful, the combat battalion of the engineer regiment must directly attack the strong defense brink with flesh and blood. Even if the Buselas Fortress was finally taken down, according to the previous French war examples, the combat engineer battalion, which served as the vanguard, would have to be reduced by at least half.

On the side, Lieutenant Jacques was also silent. As the commander of Marshal Desay, he was quietly waiting for the colonel's final reply. Suddenly, the corner of the fence blocking the command post and the entrance of the tunnel was lifted open. A naked engineer with a naked chest and a wet mud on his back ran towards Ultrasle with joy on his face, and he reported a good news to the regiment commander.

Before the engineer could sort out the military appearance, the engineer officer said excitedly: "Col. We have just walked 8 meters away from the right side of the granite rock and successfully walked under the bastion!"

Colonel Ultrasle was overjoyed after hearing this, and he hurriedly asked: "Very good, lieutenant! Is there any obstacles from other granite rocks? Also, when can the T-channel for detonation be carved?"

The second lieutenant replied: "The engineer said that based on the analysis of the currently extracted soil samples, the chances of this possibility are very small. Therefore, for up to 4 to 5 hours of excavation, we can fill the tunnel inside the tunnel before dusk."

While waiting for Colonel Ultrasle to finish the conversation with the lieutenant, Lieutenant Jacques smiled and turned to the commander of the Engineer Regiment to raise his hand to pay tribute. "Col. Please allow me to express my sincere congratulations to you and your heroic subordinates in advance. I will report this to Marshal Desay immediately."
Chapter completed!