Historically, Nanjing, as the ancient capital of the Six Dynasties and the metropolis of the Ten Dynasties, has been a battleground for military strategists since ancient times. Its advantages are various, and the geographical environment is a very important one. Nanjing, located on the south bank of the Yangtze River, has been a natural barrier since ancient times. Nanjing's geographical position in ancient times made it difficult for the northern army to cross the river. Most troops are better at land warfare, but water warfare is the weakness of most troops. Many famous water war cases in history are based on the fact that fewer people win more. For example, Battle of Red Cliffs in The Romance of the Three Kingdoms, which is familiar to everyone, is a typical war case. I will elaborate on this from several aspects.

geographical environment

As mentioned earlier, Nanjing is located on the south bank of the Yangtze River, and it has a natural barrier of the natural barrier of the Yangtze River, which makes it difficult for the northern army to attack. To attack Nanjing, it is necessary to prepare the navy, which needs money and energy. This is only the first step, and there are still many places to consider.

Secondly, the climate of Nanjing was in a warm subtropical area in ancient times, with abundant rain and humid air. Nanjing is surrounded by mountains on three sides, forming a special terrain. The moisture can't be dispersed, and it is particularly hot in summer. These climates are fatal to the northern army. Especially in summer, if you want to cross the Yangtze River from the north bank to the south bank, you have to endure the scorching sun, swaying sailboats and sultry humidity. These are really difficult for soldiers in the north. Many people suffer from heatstroke or food problems because of these weather before they set foot on the battlefield, which seriously affects the combat effectiveness of the troops.

If you want to attack Nanjing in winter, it will be a test. Winter in Nanjing is colder in history. This kind of cold is not dry cold in the north. You can carry it by putting on more clothes or cotton-padded jacket. Winter in Nanjing is wet and cold. Even if you wear a cotton-padded jacket, you can still feel the cold, and your hands and feet are easily frostbitten, which has a great impact on the combat effectiveness of the troops. Not to mention the cold rainy season, sometimes it can rain for more than a month. Wet roads and muddy dirt roads make people sick easily, which has a great influence on the combat effectiveness of troops. Many times in history, the northern army tried to attack Jiangnan in these aspects, and all ended in failure.

economic impact

Since the Western Jin Dynasty moved south, a large number of skilled craftsmen and technicians have been brought from the Central Plains, and some agricultural technologies and water conservancy improvement methods in the north have been brought to the past, which has promoted the development of the south. As an ancient capital, Nanjing has changed even more. After the Eastern Jin Dynasty, Nanjing was a relatively large city. If it is not the capital, it will have a great impact on the surrounding areas.

Nanjing has also produced many famous businessmen and big families in history. These people are good at doing business, so Nanjing's economic status is becoming more and more influential in cities in the south of the Yangtze River. This is especially true after the Ming and Qing Dynasties. The tax revenue in the south of the Yangtze River with Nanjing as the center accounts for more than 40% of the total national income. This area also brings together river transportation, commerce, salt industry and agriculture, and its economic influence is growing. All these have made the rulers of past dynasties attach great importance to Nanjing, and they all stationed heavy guards here.