A landmine is an explosive firearm deployed below or on the ground, mainly composed of a mine body and a firing device, where the mine body contains a mine shell and gunpowder. The history of the use of landmines in China can be traced back to more than 500 years ago, with the earliest record dating back to the Jiajing period of the Ming Dynasty. At that time, the Minister of War, Zeng Xian, organized personnel to manufacture landmines during the military affairs of the Governor General of Shaanxi Province, but the specific shape of the landmines is difficult to verify due to the lack of historical materials. Afterwards, landmines were widely manufactured and used in military practice. During the defense of the Great Wall along the eastern coast, the famous anti Japanese general Qi Jiguang produced a large number of landmines and deployed them in strategic passes or ambush areas, effectively enhancing the defense capability. During the Wanli period, the number of types of landmines significantly increased, with over 10 recorded in the book "Wubei Zhi" alone, including explosive cannons, aerial mines, invincible landmine cannons, self-propelled cannons, and ten thousand bullet landmine cannons. Here is a brief introduction to several representative landmines at that time. The shell of the cannon is made of cast iron, about the size of a bowl, with a charging port on the surface. After charging, it is compacted with a wooden pestle and inserted into a small bamboo tube to draw out the live wire. When in use, it is common to connect the live wires of multiple explosives in series, connect them to the fire groove of a steel wheel (a mechanical device that triggers explosions through external force), and then lead a long line from the device to be buried in the enemy's path. When the enemy steps on a long line, it will trigger the steel wheel firing device and cause an explosion. In addition to explosives, self-propelled guns and ten thousand bullet mine guns also use steel wheel ignition and detonation mechanisms. When the thunder rises from the ground to the sky, it is ignited with a spark, which is placed in a basin and on the shell of the mine. The live wire is drawn out from the shell of the mine and coiled around the edge of the basin near the spark. Several long handled knives and guns are erected on the surface of the basin as lure weapons, buried in soil to attract enemy contact. When enemy soldiers attempt to extract weapons, the spark pours over and ignites the front line, which in turn detonates the landmine. The invincible landmine cannon belongs to the artificial ignition and detonation type, and its shell is a circular structure made of pig iron with gunpowder inside. After loading, seal the mine opening with hardwood and install three lead wires into a long bamboo tube, with the tube opening facing towards the side to lead out the live wire. The landmine is buried in the enemy's path, and when the enemy enters the minefield, soldiers immediately ignite the fuse and detonate it. In the autumn of the ninth year of Chongzhen, the Qing army led by Ajige broke through the Great Wall defense line and advanced straight to Changping. At the beginning of the war, the generals of the Ming army were helpless due to chaotic command and improper tactics. Geng Shiran, who was serving as a military reserve officer in Changping at the time, requested orders in the face of danger and led his troops to survey the terrain of the Qijialing Mountains and valleys, gaining insight into the weakness of the Qing army's "ability to ride and shoot, but shorter than mountain warfare". Therefore, he secretly laid a minefield at the enemy's strategic pass. The vanguard of the Qing army swarmed towards the minefield, triggering the mechanism. "Thunder rises from the ground, smoke rises with the sky," and the sound of explosions shook the valley, causing heavy casualties. Others saw the situation and fled in panic, but Changping was saved. This battle can be regarded as a precious example of the Ming Dynasty's actual use of landmines, and also a model battle for the application of firearms and mountain defense tactics in the late Ming Dynasty. (New Society)