On November 30, 1950, the 27th Army of the Volunteer Army mobilized 5 regiments under the unified command of Deputy Army Commander Zhan Danan to launch a surprise attack on the 31st Regiment of the 7th US Division marching to Xinxingli. In terms of scale, it was only a local battle, not enough to affect the entire battle. However, under the special historical background, this battle became the most classic example of the Korean War because of the two participating troops and the final result. 
The 27th Army, formerly known as the Huaye 9th Column, was an ace unit known for its "invincible offensive ability". The first to attack the city of Jinan, the first to cross the Yangtze River, the first to enter Shanghai, the military history of the 27th Army is brilliant, and its strong ability to attack fortifications is second to none in Sanye and even the whole army. It is precisely for this reason that when Su Yu was planning to attack Taiwan and taking office as the commander of the border defense forces to resist US aggression and aid Korea, he included the 27th Army in the first attack echelon and regarded this unit as the vanguard of the vanguard. The 7th Infantry Division of the U.S. Army participated in two world wars and was known as the ace of the U.S. Army in the Southwest Pacific Theater. In particular, its main force, the 31st Regiment, once invaded Siberia in World War I, was awarded the title of "Polar Bear Regiment" by Woodrow Wilson of the United States, and personally awarded the "Polar Bear Flag". 
In the first battle of Xinxingli, the 4th Company of the 80th Division of the 27th Army infiltrated the 1100 Heights Mountain Mouth alone at the beginning of the battle, and in one fell swoop eliminated the headquarters of the 31st Regiment of the US Army, and captured the "Polar Bear Flag", staging a good show of capturing the thief and capturing the king first. In the following days of fighting, the participating units of the 27th Army launched a full-scale offensive, and finally annihilated the 31st Regiment, erasing the "Polar Bear Regiment" from the battle sequence of the US army forever. In the contest between the two ace troops, the Volunteer Army won a complete victory, and this was also the only glorious example of the Volunteer Army in the Korean War in which a regiment of the US Army was completely annihilated in a systematic manner. But at the same time, with an absolute superiority in strength and the use of all artillery units of the whole army, the 27th Army still paid the price of ** and non-combat attrition of up to 10,000 people. The Polar Bear Regiment has 3 infantry battalions, a tank company, a total strength of more than 4,000 people, 46 artillery pieces, 37 tanks, a large number of 60 or 90 rocket launchers, and an average of 2 to 8 times a day of air force fire support. The five regiments of the 27th Army struggled to eat one reinforced regiment of the US army, which was a tactical victory, but it also showed that the volunteers were seriously deficient in firepower allocation, and the artillery fire of an army was even difficult to compare with that of a regiment of the US army. 
This battle with the Polar Bear Regiment is also a microcosm of the entire Battle of Changjin Lake and even the Korean War. The lack of heavy firepower of the Volunteer Army also made the US army's circular position composed of armored vehicles, tanks, heavy artillery, and machine guns almost impossible to break through. The main reason why the three armies of the 9th Corps could not block a 1st Marine Division at Changjin Lake and paid huge losses was that the inferior firepower completely offset the superiority of the Volunteers in terms of strength and tactics. But it was precisely this disastrous victory in the Battle of Changjin Lake that accelerated a thorough innovation in the firepower configuration of the Volunteer Army. At the beginning of April 1951, the 48th Artillery Division of the 21st Army secretly entered the Korean War, which was also the first rocket artillery division of the Volunteer Army. Before entering the DPRK, the 21st Division underwent a five-month training, received guidance and assessment from the Soviet expert group, and was equipped with 120 "BM-13" Soviet-style rocket launchers, also known as the "Katyusha". 
The Katyusha was the most advanced self-propelled rocket launcher in the world at that time, it had 8 launch slides, and a single salvo could fire 16 rockets with a caliber of 132 mm, with a maximum range of 85 km. Even more terrifying is the fact that the rocket launchers are truck-loaded, extremely flexible, and take about 5 to 10 minutes to reload once, and 7 to 10 seconds for a salvo. With a regiment as a combat unit, the Katyusha can fire 384 rockets in an instant, which is enough to cover all targets. The arrival of the Katyusha has given *** full confidence, and the commander of the Volunteer Army once said: "Now the Volunteer Army has such the most advanced and modern Katyusha rocket artillery!."The United States has not yet done so, and we have to look for fighters well!Play to the advantage of rocket artillery!Unexpectedly, a mountain of lightning strikes at the enemy!Destroy the enemy's living forces in large numbers. "On September 1, 1951, the 203rd Regiment of the 21st Division was ordered to be attached to the 235th Regiment of the 79th Division of the 27th Army operating on the Eastern Front to carry out a counterattack against the US 7th Division. In this battle in which the 27th Army and the US 7th Division met in a narrow way, Katyusha rocket artillery appeared on the Korean battlefield for the first time and became the real protagonist of the war. After the battle began, the 203rd Regiment's 24 Katyusha suddenly launched a salvo against the American troops attacking our positions, and 384 rockets smashed into the American troops like thousands of fire dragons. The most violent**, the smoke of gunpowder that covered the sky and the sun, the scorched earth on the US position, and the fragmented wreckage and burning flames everywhere. 
Hong Xuezhi, deputy commander of the Chinese People's Volunteer Army, once described the scene of the Katyusha salvo as follows: "The 21st Artillery Division was launched on time, and the artillery fire formed countless flames, flying towards the enemy position like a whining wind, red through half of the sky, covering all the enemy positions of several square kilometers, and the enemy positions quickly burned. Our Katyusha rocket artillery 21st division fired two more in a row, and at this time the other artillery was still firing. When the battle was over, the enemy's position burned into a sea of fire, the smoke and dust rising from the ground were red, and the clouds rolling in the sky were also red ......"Two battalions of American troops were completely routed by the Katyusha, and the combat losses amounted to more than 700 people. It was the first time that the American soldiers who had been beaten to death encountered such a scene on the Korean battlefield, and they exclaimed as if they had witnessed the end of the world: "The volunteers used atomic cannons!"In the subsequent Battle of Shangganling, the 209th Regiment of the 21st Division was once again ordered to support the front-line battle that was in a stalemate. In the Volunteer Army counterattacked 5979 Highlands and 537During the battle at the North Hill position on the 7th Heights, after a volley of Katyusha fired, the American positions fell into a deathly silence. The volunteer fighters rushed to the position and found that almost all the American troops of the two battalions on the position had been killed in this round of shelling. Only two American soldiers had their breath left, and they were all knocked unconscious by the heavy shelling. In the whole battle, the joint ** killed and wounded 1,500 people, while our army only **70 people. 
The American army was completely blinded by the Katyusha, and our volunteer soldiers saw such powerful artillery for the first time. At the beginning of the battle, it was covered with Katyusha rocket artillery, which inflicted immeasurable damage on the American troops, and such a heroic battle made the volunteer soldiers extremely excited. At any time and in any place, if the infantry, tanks, and combat vehicles of the Volunteer Army encounter the Katyusha convoy of the 21st Division, they will take the initiative to give way and cheer to pay tribute to this group of "most mysterious comrades-in-arms". The fighters all know that if there is a Katyusha, the US army will suffer. The Katyusha was originally known as the "BM-13 rocket launcher" and first appeared in the Great Patriotic War of the Soviet Union. Because this new type of ** was required to be kept strictly secret at that time, the Soviet Red Army did not know its official name, so it named this powerful rocket artillery with the female nickname "Katyusha". The Germans, who were the first to suffer from the Katyusha, called it "Stalin's organ" because of the sound of this rocket launcher similar to that of an organ. In the Volunteer Army, Katyusha also has two professional titles, one is "121" (Katyusha's code name), and the other is "Jiaojiao Cannon". Compared to ordinary fighters, the name "Jiaojiao" is more popular. This nickname has two meanings, one is to say that Katyusha's achievements are proud, and its destructive power on enemy positions is great, which has made the volunteers have made a qualitative leap in firepower. The second is that the Katyusha is very squeamish in its use, with a large shelf, a large artillery, and a large pomp, and when it moves, it is earth-shattering, and it is easy to expose its position in front of the US forces that occupy air supremacy after launchingAnd because Katyusha cannot be produced in China, it is all supplied by the Soviet Union, which can be described as an inch of gold. At that time, there was a saying that one shell of Katyusha was worth 6 taels**. It is precisely for this reason that ** attaches great importance to these "squeamish babies", and has repeatedly emphasized: "Which corps and which army your rocket artillery regiment belongs to fight, must be approved by me." ”
After Katyusha entered the court, he repeatedly performed miraculous feats, destroying an average of 3,000 enemies in each battle, which greatly increased the prestige of the volunteers. The U.S. military, which once relied on powerful firepower to show off its might, has been torn off the last fig leaf, and they no longer have any advantage in the confrontation with the volunteers. An invincible volunteer army and a powerful Katyusha completely put the Americans at the negotiating table.