Ten thousand I am across the heavens

Dividing the underground tunnel defenses into different layers allows for the maximum detection of the enemy while simultaneously preventing them from approaching.

Underground vacuum pipes are typically straight. Therefore, these ring-shaped pipes often encircle the underground vacuum pipes, forming concentric cylinders. These cylinders, in turn, resemble an onion, with one ring inside the other.

This formed a series of concentric circles that were not connected to each other.

This unique structure ensures that no matter how one travels within the pipe, the distance to the vacuum pipe will not decrease. Therefore, even if the enemy captures the vacuum pipe, the amount of excavation work required to dig inwards will not be reduced.

During the battle, both sides continuously evolved their offensive and defensive technologies.

In the very beginning, within these underground tunnels, there were only hardened walls and no additional facilities. They primarily served as troop transport routes, used to quickly detect enemy movements and swiftly dispatch troops to intercept them.

However, in subsequent battles, it was discovered that although vacuum tubes could quickly assemble troops, the commanders of the Shanhe Republic were usually at a disadvantage in terms of troop strength in the early stages of the battle.

The frontline commanders quickly summarized their experience and identified the problem: even though commanders in different defense zones were in communication with each other, and the zones were directly connected by tunnels allowing for rapid movement and even teleportation in emergencies, mobilizing forces still took time. The attacking side would inevitably amass a large force, putting the defending side at a disadvantage in the early stages of the battle.

Moreover, most of the vacuum tunnel area needs to be defended. It's impossible to mobilize troops from afar, to prevent the enemy from using feints. This situation puts the initial forces at a disadvantage.

Therefore, in subsequent construction, underground tunnels were not only used for transportation but also transformed into defensive structures, albeit different from surface defenses. These tunnels offer a more proactive form of defense.

The tunnel would extend into winding, wavy pipes, allowing mechanical soldiers to be stationed within them. These irregularly shaped pipes, like the wires of a steel wool ball, were arranged haphazardly and loosely on the outer edge.

Within these areas, mechanical soldiers can be stationed anywhere. The enemy, regardless of their choice, will inevitably enter this chaotic region.

This area was their own designed territory. Once inside this chaotic and complex network of pipes, the enemy would face two choices: one was to attack along the pipes, which would reduce the time spent on earthwork; the other was to go directly through the pipes, avoiding the need to dig through the soil ahead, thus saving even more time.

However, this also presents a significant problem: the terrain within the tunnels is pre-designed by the enemy. Advancing along this terrain would likely result in plunging directly into an enemy ambush, leading to heavy casualties.

However, if one ignores the tunnel and continues digging along their predetermined route, they may still come into contact with it. The moment they enter the tunnel is the moment when they are most likely to be ambushed.

Either of these two options could result in significant casualties. However, if a choice must be made, there is a third option: bypass all tunnels altogether, completely abandoning their potential convenience. Instead, dig a road directly into the tunnel-free area.

This approach does avoid falling into an ambush, but it doesn't prevent surprise attacks. The intricate network of tunnels, like a steel wool ball, means that even with careful maneuvering to avoid every single tunnel, the excavated tunnels will inevitably get too close to the defensive structures deployed by the Shanhe Republic. In such situations, Shanhe Republic soldiers can quickly dig tunnels with minimal earthwork and launch a surprise attack.

This would be disastrous for an army on the march. Even more problematic is that being connected to these tunnels means their logistics could be vulnerable to a surprise attack.

Even if an attacking army travels as lightly as possible, it still requires a certain level of logistical support. If its supply lines are completely cut off, its combat effectiveness may remain unchanged in the short term, but it will still decline over time.

This new defense system was proposed by a previously unknown real-time strategy player. After testing and confirming its effectiveness, it was subsequently deployed in large numbers around vacuum tubes.

Meanwhile, their adversaries are constantly evolving in the course of war. Compared to the primitive firstborn, they now possess a large number of commanders who are inherently intelligent. Even if these individuals are somewhat obsessive and their overall abilities are far inferior to those of the large-scale army commanders in the rear, they still demonstrate basic human qualities in order to find solutions when faced with problems.

Therefore, they also began to equip their attacking forces with new weapons. To be precise, they equipped their excavation equipment with new gear.

They equipped their tunnel with a hard outer shell, similar to what a tunnel boring machine does when excavating underground. While digging, they simultaneously laid a rigid composite material shell around the tunnel. The shell itself didn't impede the excavation, but this relatively hard shell made digging take longer. Meanwhile, the internal sensors would immediately transmit a signal if damaged.

The troops inside the tunnel will handle the signal transmission area differently depending on the actual situation.

One approach is to quickly move the troops to the side of the signal location, and then prepare to ambush.

One ambush strategy involves flooding tunnels with large quantities of a fast-drying adhesive liquid, similar to super glue (like 502), which dries much faster and solidifies in less than a second. This liquid is stored in high-pressure tanks and released the moment the enemy breaches the outer shell. This causes the enemy's advance troops and excavation equipment to be instantly frozen in solid form. Without room to maneuver, even the most powerful drills will struggle to penetrate and will likely become stuck.

The tunnels, filled with this hardened material, would be completely blocked, forcing the enemy to dig them anew if they wanted to pursue. Re-digging would take far too long. If the enemy were to dig forward while simultaneously backfilling the tunnels behind, they would never be able to catch up. Therefore, in such a situation, the only option would be to retreat. Utilizing the advantages of the complex underground fortifications, the enemy could then relocate to another attack point, launch a surprise attack, and disrupt the enemy's offensive forces.

In this back-and-forth struggle, the Earth and Wood system, which had long since declined within the Republic of Shanhe, suddenly shone brightly here.

[To be continued]

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