In ancient times, both the Nanfei River and the Dongfei River were called Fei Water (*Fei Shui*). One flowed into the Yangtze River and the other into the Huai River, nurturing the two historical cities of Hefei and Shouchun. The Nanfei River and the Dongfei River converge near Hefei, and the name Hefei comes from this water. The "Battle of Feishui" made Fei Water famous throughout the world. Among them, the Nanfei River, also known as Shi Water, passes through Hefei city and flows into the Yangtze River via Chaohu Lake, being the "Mother River" of Hefei.

Anhui suffers from frequent floods and has always been a poverty-stricken disaster area. Chen Ke knew that after the liberation, the Republic paid a huge amount of manpower and material resources to govern the Huai River, purely relying on a huge net investment of astronomical figures to tame the Huai River, which took the Republic twenty years. If Anhui hadn't been a hot area for revolution between 1907 and 1911 in history, Chen Ke wouldn't have dared to set the base area in Anhui initially.

It wasn't until Chen Ke personally arrived in Anhui that he realized he had made the mistake of "carving a mark on the boat to find the sword" (using static measures for changing conditions). The Anhui floods faced by the Republic were different from the Anhui floods in 1907. First of all, although the Manchu Qing was rotten, it at least managed the river channels. Since the fall of the Manchu Qing, the Beiyang government occasionally managed the Huai River, but the subsequent Baldy Chiang (Chiang Kai-shek) regime had no interest in managing the Huai River.

By 1938, Baldy Chiang even ordered the bombing of the Huayuankou embankment. The Yellow River rolled south, forming a large "Yellow Flood Area" in southeastern Henan. The Yellow Flood Area not only devastated the people of Henan, but the water of the Yellow River flowing south rushed directly into the Huai River. Until 1947, in order to stop the PLA's offensive, Baldy Chiang began to rebuild the Yellow River embankment, hoping to turn large areas of shallow river channels into difficult "barriers." Chen Ke was a native of Zhengzhou, and Huayuankou was in Zhengzhou. He often rode bicycles to the Yellow River with friends during holidays. He was extremely familiar with this history.

From 1938 to 1947, nine years of Yellow River flooding had another direct consequence: the Yellow River deposited more than one billion tons of sediment in the plains and river channels every year. More than half a century has passed, and the people and professional workers on both sides of the Huai River are still working hard to digest and discharge these leftover substances. Experts even vividly compared the Huai River to a "river without a bottom," almost reaching the point of "turning pale at the mention of Yellow." They said that the main stream of the Huai River had to climb a slope more than two meters high starting from Bengbu to enter Hongze Lake, and Hongze Lake had long been a suspended lake full of crises.

Since the formation of the Yellow Flood Area, Anhui, which originally had serious floods, suffered heavy waterlogging with heavy rain, light waterlogging with light rain, and drought with no rain. Chen Ke never understood why some people still flattered Baldy, nor did he know if these people had the face to face those common people who struggled painfully and lost their lives in the Anhui floods.

It was 1907 now. Although the Huai River problem was serious, it hadn't reached the tragic level of later generations. At least in Chen Ke's view, Anhui in the Huai River basin was still an area with smooth waterways and convenient navigation. In the Anqing Campaign at the beginning of the year, if Chen Ke hadn't been afraid of alerting the enemy after attacking Hefei, the most economical route for the troops would have been to take the two Fei rivers and enter the Yangtze River through Chaohu Lake. Now Li Yuanhong's troops took the completely opposite path; they entered Chaohu Lake from the Yangtze River and reached Hefei via the Nanfei River.

At this time, the Nanfei River was still very wide. According to the hydrological data captured by the People's Party from Anqing and Luzhou Prefecture and the results of their own surveying, the river bottom of the Nanfei River was 30-80 meters wide, with a water depth elevation of 6-6.5 meters, 7 meters in the high-water period, and about 8 meters in the flood period. If the warships of the Hubei New Army were not afraid to sail along the fixed route in the center of the river channel, they could definitely pass smoothly. The People's Party now lacked heavy artillery and could not pose an effective threat to the navy of the Hubei New Army.

The high-level theoretical training of the People's Party had basically completed the concept of "scientification," and no one among the high and middle-level comrades believed in the Dragon King anymore. As soon as Chen Ke proposed "Iron Lock Across the River," Hua Xiongmao explained the concept of cement piles in detail, and everyone started working immediately. When the troops moved out this time, Chen Ke had actually completed his plan long ago, so he specially brought You Gou along. You Gou was directly responsible for cement, glass, and ceramic production. She had long wanted to come to the battlefield to have a look, and this time she found a place to use her skills.

The soldiers were very familiar with Secretary You Gou, and many officers had worked under her. With the female secretary leading the team personally, everyone was full of energy. At the three shallowest parts of the Nanfei River channel, mixing frames were fixed with boats and rafts. Small cement piles were sunk first, followed by large cement piles. In one and a half days, the water depth at these three obstacles was filled from more than five meters to one and a half meters. Non-motorized small boats could pass freely, but the steam-powered ships of the Hubei New Army couldn't pass at all.

Without cement and cement pouring technology, creating a barrier at the bottom of the river in a short time would be a daydream. Without cement, stones would have to be used. Small stones would be washed away by water, and large stones couldn't be transported in a short time. With cement, it only took a certain amount of time to build obstacles of any size. Moreover, You Gou didn't just work; she also conducted training on cement knowledge. The unit making obstacles this time was the newly established "Engineering Corps" of the base area. Chen Ke set the rank of the Engineering Corps extremely high. The Engineering Corps would have jurisdiction over engineering troops and railway troops in the future. Chen Ke stated clearly that the Commander-in-Chief of the future Engineering Corps would be only half a level lower than the Minister of Defense. That is to say, the Commander-in-Chief and General Political Commissar of the Engineering Corps would directly become members of the Military Commission and strong competitors for the Vice Chairman of the Military Commission.

Now the Engineering Corps was temporarily subordinate to the Commission of Science, Technology and Industry for National Defense. The Director and Political Commissar of the Commission were temporarily held by You Gou concurrently. So You Gou, a woman without military rank, also controlled a powerful paramilitary force. No one in the Military Commission dared to gossip about this, because this Engineering Corps was not equivalent to "sappers." The "sappers" of the People's Party were combat troops. The engineering soldiers were expanded from the cement-burning unit personally led by You Gou last year. This was a unit brought up by You Gou single-handedly.

Some local civil affairs cadres worried that these barriers would hinder future channel navigation. Zhang Yu directly showed everyone the new diving equipment made by the People's Party. This was a ship-use diving equipment. The most striking items in the diver's full set of equipment were a hand-cranked air supply machine, an iron respirator with a glass observation window, and an air supply tube made of silk and bamboo tubes. With this set of equipment, divers could set explosives underwater. After the Battle of Hefei ended, these three underwater interception walls would be blown up. After the blasting, larger obstacles would be salvaged to reinforce the river channel, and small pieces would be left at the bottom of the river.

Zhang Yu said to the enlightened comrades, "Our People's Party has always stressed having a beginning and an end in doing things. Secretary You Gou has long considered such matters."

Regarding Zhang Yu's flattery, You Gou just laughed heartily, then commanded the engineering troops to evacuate the construction site. More than a year ago, when Chen Ke personally led the team to drive boats to rescue the people, there were only six or seven loyal Party members Chen Ke could trust. Zhang Yu had also been You Gou's deputy. You Gou knew very well that apart from laughing heartily now, any word she said would be superfluous.

The People's Party talked about science themselves and also attached importance to intelligence collection. Their only worry was whether Li Yuanhong had forgotten all the things he learned in the Beiyang Naval Academy back then. If Li Yuanhong marched forcibly without talking about science, the ships of the Hubei Navy would definitely run aground, which would only delay everyone's time. If Li Yuanhong talked about science and conducted detailed channel surveys, he would obediently divide his troops into two routes. The People's Party had already opened the bag, waiting for the Hubei New Army's land forces to walk right into the trap.

Li Yuanhong undoubtedly hadn't forgotten his old profession completely. The leading survey ship soon reported the abnormality at the bottom of the river. After receiving this news, Li Yuanhong felt an indescribable discomfort. He knew his "teacher" Yan Fu was now a high official of the People's Party, and this military operation of the Hubei New Army was known as "exterminating the Yan-Chen Bandit Gang."

Li Yuanhong went to check the front personally. On the wide water surface of the Nanfei River, a neat water pattern appeared. This water pattern divided the narrowest part of the Nanfei River into two. That was the undercurrent formed on the water surface when the water flow of the river channel was suddenly blocked by the underwater obstacle traversing the river channel and forced to flow upward. Li Yuanhong came from the navy and could understand the significance of this obstacle even more. To be able to create an obstacle tens of meters long—what organizational ability was this? Li Yuanhong was shocked.

Of course, if this shock were known by the officers and soldiers of the Engineering Corps under You Gou, they would probably laugh at Li Yuanhong for making a fuss. The engineering soldiers only used more than two thousand bags of cement and more than a thousand bamboo cages. More than two thousand bags of cement could be produced in the base area in five days. Weaving these double-layer bamboo cages only took five days. The reed mats used as mold partitions could be reused, consuming even less time. Compared with this siege, the engineering soldiers generally believed that the construction of various water conservancy projects they participated in was the headache-inducing work. With rich surveying data and equations, calculating the water flow speed and impact force, simply piling up a temporary obstacle didn't involve much technical content at all.

Facing this obstacle, Li Yuanhong was scared. He summoned the staff officers to discuss the matter. Now between the Nanfei River and Hefei, the scouts of the Hubei New Army passed unimpeded. Every message they reported was "no trace of the People's Party found." The staff officers couldn't explain clearly why the People's Party built such an obstacle. The only certainty was that with this obstacle, the Hubei New Army had to get off the boat and walk to Hefei fifty *li* away. This indeed took a lot of time, but small boats and most official boats could pass this underwater obstacle. That is to say, this obstacle only blocked the steam-powered gunboats of the navy.

"Lord Li, speed is precious in war. We came so fast; presumably, the rebels want to use this method to block us, right?" A staff officer put forward this view.

"How long does it take you to build such a thing underwater?" Li Yuanhong asked.

The staff officer was immediately speechless. Building such a thing was definitely not the work of one day and one night.

"My Lord, I'm afraid this thing was built by the bandits long ago. Moreover, walking fifty *li* is just one day's time. Now scouts come and go like wind. Regardless of what the bandits think, after occupying Hefei city, we can accomplish a lot. Why worry about such a small obstacle?" An impatient officer suggested.

Although Li Yuanhong thought so in his heart, he felt he couldn't help but be cautious. After thinking for a long time, Li Yuanhong said, "Stay where we are; let's watch first."