Ancient city gates are very tall, thick, because the ancient level of social development is relatively low, the construction of the city gate is very important, has always been highly valued by the rulers, because the city gate in the war years can defend against the enemy's attack, in peacetime can also prevent the attack of bandits and robbers, so the city gate without exception is built and the city wall is closely integrated, once the city gate is closed, the whole city is like a huge brick.
In that year, the Eight-Power Alliance attacked Beijing, and the invaders already had modern firearms, guns and cannons, but it was not easy to attack the city, because the walls of Beijing City were thick and high, and the people of Beijing City sent a message to the Eight-Power Alliance -- the sewers under the Guangqu Gate were undefended and could be entered.
The vast city of Beijing was thus occupied by the invading army, burning and plundering, doing no evil, the prosperous capital, the capital of the ancient civilization immediately became a hell on earth, and the leader of the invading army, Wadhi, also sat on the dragon chair of the Emperor of the Qing Dynasty in the Taihe Temple.
You say that even an undefended sewer can be a fatal wound to the destruction of the city, can there be a path in addition to the city gate? So it is impossible to leave a path, and if you stay, it is to die.
Zhang Fei fought zhang Guo at Wakou Pass and never broke through this pass, only to find that several civilians came from the lower road and inquired about a small road leading directly behind Wakou Pass, so they seized Wakou Pass. This is just a small road behind the Tongwakou Pass, and it is still impossible to enter the Wakou Pass, so Zhang Fei seized the pass, which shows the harm of the path. Zhang Hao had just arrived here unfamiliar with geography, otherwise he would have to fortify.
This is true in ancient China, the same is true in the ancient Western world, the walls are tall and thick, the gates are strong, and Constantinople, the capital of the Eastern Roman Empire, which lasted for nearly a thousand years, was protected by such walls and gates, and in the history of nearly a thousand years, except for the Crusades of the Fourth Crusade, no one could conquer the city, so the emerging Ottoman Empire did not intend to attack there, thinking that the cost was too high.
However, with the expansion of the Ottoman Empire, the increasingly dangerous position of Constantinople, coupled with the development of firearms, the Ottoman Empire was determined to conquer the fortress, so it launched an attack on it, but the progress was not smooth, and finally found that there was a small door for cooks to enter and exit, called the Kekaporta Gate, which was undefended. Thus, the Ottoman army entered Constantinople from the Gate of Kecaporta.
On 29 May 1453, after a two-year siege, Mehmed II conquered Constantinople, the Byzantine Emperor Constantine XI was killed in battle, and Constantinople was renamed Istanbul.
A small road that destroyed an Eastern Roman Empire that lasted for nearly a thousand years is a bit of a cost! Who would have thought that a small door path dedicated to the entry and exit of cooks would become the last straw that broke the back of the camel in the Eastern Roman Empire. The enemy besieged the city for two years, using all means of attack, including artillery, and failed to conquer Constantinople, but was conquered because of the undefended road and small door, and a thousand-year-old empire collapsed. Who would dare to leave a trail outside the city gates?
In the "Romance of the Three Kingdoms", Deng Aidu Yinping Xiaolu attacked Chengdu and finally destroyed the Shu Han regime, which is also the same reason, but that small road is the path to Chengdu. At the beginning, it was fortified, and Zhuge Liang not only sent a thousand elite troops to fortify, but also erected a monument and carved words to predict the fate of Deng Ai. However, Liu Chan withdrew the thousand defenders, leading to the rapid demise of the Shu Han regime.
From the history of ancient China and foreign countries, it can be seen that the harm of leaving a trail outside the city gate is very great, so all countries do not leave a trail outside the city gate. If there are naturally formed paths, they will be fortified. Therefore, from these stories, it can be seen that after the ancient city gate was closed, it was impossible to enter and exit the city.