Among the three archipelagos of the Tang Empire, the Tonga Islands and the Hapai Islands are coral reef islands, with flat terrain and an altitude of only about 10 meters, which are only suitable for living and working.

Only the Vava'u archipelago is a volcanic archipelago and the highest archipelago. Among them, Vavau Island is the main island, and the northern volcanic group is about 500 meters above sea level, which is the only commanding height of the Tang Empire, where the Yanjing Fortress is located, and Xiangxia protects the safety of Yanjing.

As one of the four cities of the Tang Empire, Yanjing's military status was the highest, and Zhang Meng concentrated all his heavy industry and military industry in Yanjing, relying on the protection of Yanjing Fortress.

The Vava'u Islands were the first place where Zhang Meng began construction. At this time, the prototype of Yanjing's city has basically been seen. Roads cut the island into regular grids, the foundations of thousands of buildings in residential and commercial areas have been watered and piled, and the tropical forests where industrial zones are located have been cleared.

The fastest was the Vava'u Island Fortress, which has now been renamed Yanjing Fortress. Yanjing Fortress is one of Zhang Meng's key military projects, because Yanjing Fortress is located above the volcanic group, the volcanic lava itself is extremely strong, and it is a natural protective shield against attacks from the sea and air. There are countless volcanic caves inside, most of which can be directly passed by personnel and weapons, and the rest only need to be excavated.

Because there are many natural karst caves and volcanic rocks are strong, the underground bunker fortifications of Yanjing Fortress only need to be dealt with simply to meet the requirements of large-scale fortress underground fortifications of the same level abroad.

Four main batteries, twelve second-class batteries and six third-class batteries were set up in the upper part of the Yanjing fortress, and about 200 fortress guns were installed in Jihua.

The construction of the second and third batteries had already begun, but Zhang Meng asked for a moratorium because he was still waiting for an opportunity, that is, the outbreak of the global economic crisis, when arms procurement was relatively easy and cheap.

Now that the Shijie economic crisis has broken out, Zhang Meng's opportunity has come.

In fact, Zhang Meng already had a goal in mind, and he knew that the most powerful fortress fort during World War II was not the well-known Maginot or the famous Singapore fortress, but the most practical Soviet fortress Vladivostok.

In Zhang Meng's view, practicality is the first thing to consider. At present, almost all the mainstream fortress artillery in various countries are large-caliber fortress guns made by Krupp in Germany, on the grounds that they are powerful. However, this kind of fortress cannon performed mediocre in actual combat, and the firing range was the biggest obstacle.

During World War II, the Soviets dismantled the battleship's main guns on the Vladivostok fortress and installed them on the fortress battery, which had a wide firing range, 360 degrees of all-round rotation, and a high and low elevation angle of plus or minus 37 degrees.

Zhang Meng was most worried that the Tang Empire's future support for the national army to resist Japan would lead to the Japanese army's crazy retaliation, so he had to prepare for defensive measures in a targeted manner, rather than blindly worshipping the so-called Krupp cannon.

Zhang Meng has locked in a large-caliber artillery supply company, which is the Ghana Navy naval gun manufacturing plant under the French Mediterranean.

The most sensitive large-caliber artillery for the fortresses was imported from the French, Mediterranean, Ghana arms company, at the expense of Ecuador and other Central American countries as intermediaries in third countries.

Of course, Zhang Meng's choice of the French Mediterranean Ghana Arms Company was also an overall consideration. This company provided a triple 506 times the diameter of the 406 mm DK300 naval gun system, which was built as a mature naval gun system in the late World War I, and was once installed on the Richelieu-class battleships by the French Navy, but after World War I, France's national strength was seriously weakened, and the construction of Richelieu-class battleships was repeatedly delayed. Seeing that the French Navy had chosen a 350-mm Dunkirk-class battleship, the Ghanaian company was forced to look for an overseas buyer. But in the treaty era, there was no buyer for this large-caliber main gun, and when the global economic crisis broke out, it was about to rot in his hands, and no matter what the buyer came from, when Zhang Meng sent someone to contact them, they immediately agreed.

Zhang Meng spent only 15 million dollars to get four DK300 naval gun systems, as well as two hundred rounds of 406-mm shells. You must know that the cost of materials for these four sets of naval artillery systems and shells alone will cost $20 million, and the actual cost will be about $23 million if you count the messy expenses such as labor costs. If it weren't for the fact that the Ghanaian company was short of funds and urgently needed working capital, this price would never be enough, and Zhang Meng would undoubtedly take advantage of it.

Deploying these four triple 506-caliber 406mm guns on the four main heights of the fortress is equivalent to placing an unsinkable super-dreadnought battleship on Vava'u Island. If at sea level, the maximum firing range of the DK300 naval guns will not exceed 40 km, but at an altitude of more than five hundred meters above sea level, firing from a high position, its range will theoretically be doubled, enough to cover the entire island of Vava'u and the near sea zone. In particular, this naval gun adopts a 50-fold diameter barrel design, and there is no roll and turbulence at sea, and its hitting accuracy will be greatly improved. Coupled with its 500 mm thick armor protection and 360-degree rotating shooting ability, if it relies on the reinforced concrete protective layer of the fortress, Zhang Meng believes that even if the devil's Yamato battleship runs over, it will still beat it all over the ground!

The core stake of Vava'u Island is in the southern part of Yanjing, which is surrounded by the sea on three sides and backed by fortresses, so the importance of the fortress is self-evident.

Because it is surrounded by the sea on three sides, the rotation performance of the main gun of the fortress is very important, which is one of the main reasons why Zhang Meng chose the large-caliber naval gun as the main gun of the fortress.

The fort also includes eight 240 mm cannons, 16 152 mm cannons, 20 80 mm anti-aircraft guns, 60 M2 heavy machine guns, and ten base ammunition to accommodate the fort's four triple 406 mm guns.

Although Zhang Meng knew that it would be difficult for a strong air threat to appear in the Central Pacific, he was still prepared to fight against at least four aircraft carrier battle groups at the same time, so he equipped the fortress with all-round anti-aircraft artillery at high, medium and low altitudes, mainly 128 mm, 88 mm and 47 mm anti-aircraft guns, and built an air defense fire network covering the entire Vava'u Island.

According to the design plan of the fortress engineer Riva hired by Zhang Meng, the entire fortress project of Vava'u Island was completed in June 1931, and at least 2,300 people were needed to support the normal operation of the fortress.

The entire fortress of Vava'u Island was required to fund $29 million, and the cost of weapons and equipment accounted for more than half. Zhang Meng's most shrewd thing is that he only paid a small deposit and used cash on delivery settlement. Although the middleman will take a certain commission, Zhang Meng believes that it is worth it and the risk is minimized.

Zhang Meng considered that in case his actions on Vava'u Island alarmed the powers, in case he found out that he was the culprit and came to retaliate, because the entire Vava'u Islands did not have the ability to resist the attack of the powerful Japanese Navy during the construction of the fortress, Zhang Meng purchased 5,000 mines from France in one go, and densely laid mines in the 200-kilometer sea area around the Vava'u Islands to prevent enemy ships from approaching, and opened up several hidden new shipping lanes alone.

At the same time, dense minefields have also been laid around the islands where Chang'an, Jinling, and Daxing are located.

Although Zhang Meng made some fuss, in the eyes of others, Zhang Meng was right to do so, because he was careful to sail the ship of ten thousand years.

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