In July 1938, Chiang Kai-shek ordered the Seventeenth Route Army to be reorganized into the 31st Army, with Sun Weiru as the commander of the regiment, and all the units under his command, except for a brigade that had been detained by Jiang Dingwen and never returned later, all left Shaanxi and went to the first line of the anti-Japanese resistance in southwestern Jin, with the task of holding on to Zhongtiao Mountain and defending the safety of the Yellow River. Chiang Kai-shek strictly ordered Sun Weiru not to retreat across the Yellow River under any circumstances and to desperately defend it. Soon, the 31st Army was changed to the Fourth Army, and Sun Weiru was appointed as the commander-in-chief.
The reason why Chiang Kai-shek transferred all the Fourth Army to Zhongtiao Mountain was that in addition to relieving Sun Weiru from his post as chairman of the Shaanxi Provincial Government and squeezing out the former Seventeenth Route Army from his homeland, he also had another intention. At that time, a japanese pictorial newspaper had a cartoon depicting Chiang Kai-shek's conspiracy to the fullest. The cartoon depicts the troops holding on to Mt. Nakajo dressed in worn-out clothes, carrying torn guns on their shoulders, and marked with the words "Miscellaneous Cards." In front of them were the Japanese troops, followed by well-dressed and well-equipped Chiang Kai-shek troops, holding bayonets and poking at the backs of the "miscellaneous cards" with bayonets. Although this cartoon is a propaganda poster of the Japanese army, it portrays Chiang Kai-shek's sinister intentions in such a way as to eliminate the Seventeenth Route Army. To this point. General Sun Weiru knew very well, but he could not openly confront Chiang Kai-shek. On the one hand, he was always worried about the life of General Yang Hucheng, who was in custody, and he was afraid that Chiang Kai-shek would find an excuse to harm General Yang; on the other hand, he was well aware of the importance of holding on to Zhongtiao Mountain to defend the land of Sanqin from being trampled by the Japanese army. He encouraged the troops to put the great national righteousness first, heroically kill the enemy, and swear to defend their hometown from aggression to the death. Some of the old subordinates and generals of the Seventeenth Route Army also blamed him to his face, believing that they could not obey Chiang Kai-shek's orders, took the unit created by General Yang Hucheng to fight with the Japanese, and acted as cannon fodder for hundreds of thousands of Chiang Kai-shek's well-equipped troops who were well-equipped behind them. General Sun Weiru was silent, he was bitter and lonely, and he could only make up his mind to fight to the death. Yu will repay the kingdom with his flesh and blood, sacrifice his life to reject the Japanese Kou, and vow to fight the Japanese to the end! But smelling the water of the Yellow River roaring, do not ask Ma Ge to wrap the body back! ”
With the cooperation of the air force and artillery, the Japanese army concentrated tens of thousands of troops in several divisions and regiments, and in just two years, carried out eleven rampant attacks on the zhongtiao mountain defense area, of which the "bloody battle of Yongji", "The Battle of June 6", and "The Battle of Wangyuan" were the most tragic and tragic! There have been hundreds of battles, large and small, and the battle situation has never been fiercer, sometimes for a mountain, a village and a town, repeatedly competing, and changing hands several times. The Japanese offensive was strong and the number of people was heavy, which often caused casualties to the entire battalion and company of the Fourth Army holding its position. Faced with such a difficult situation, General Sun Weiru ordered the defense line to be shrunk, the troops to be concentrated, and the attack was flexible, and suspicious troops were sent behind the enemy to fight a movement war and a surprise attack, so that the Japanese army could not take care of each other from end to end, and the overall advance could not be advanced. During the past two years, the Japanese army has frequently changed its battle plan and replaced its commanders, and the more anxious it is to cross the Nakajō Mountain, the more it is unable to move forward, and the operational report reported to the Japanese military department has to claim that "although the units guarding Nakajō-no-Chi na are miscellaneous cards, their combat effectiveness is quite strong and they cannot be lightly attacked." Sun Weiru led all the officers and men of the Fourth Army to fight to the death without the cooperation of friendly support and the extreme shortage of military supplies, and always stood majestically on the Zhongtiao Mountain at a heavy cost of nearly 2/3 casualties (21,000 killed), effectively curbing the overall operational attempt of the Japanese army to open up central Asia and the German army, defending the homeland of Guanzhong with flesh and blood, and expressing the bold loyalty of the three Qin disciples.
At that time, the Shaanxi newspaper said that "the whole northwest was stabilized, thanks to the hard support of my heroic soldiers on the north bank" was not a false statement. The Japanese army regarded Zhongtiao Mountain as the "blind intestine" of the North China Battlefield, and the people of the whole country called the Fourth Army "Zhongtiao Iron Pillar". Progressive journalists from all over the world and delegations from all walks of life have come to Zhongtiao Mountain. With tears in their eyes, they comforted the officers and men; they praised everywhere in an unprecedented pomp and circumstance. Forced by the situation, Chiang Kai-shek also had to praise his achievements in the War of Resistance. General Sun Weiru smiled, and he wrote "Man Jiang Hong. Zhongtiao Mountain Anti-Japanese" is a poem. In the words, he generously chanted: "Immediately in the middle of the article, the long wind rises, the yuanyuan generation drum", "the old and new hate, counting from the beginning, turning the tide as a mainstay", complex moods, tragic feelings overflow between the lines. This not only portrayed his own spiritual outlook at that time, but also expressed the heroic ambition of the generals of the whole army to fight to the end in The Zhongtiao Mountains and eliminate the Japanese Kou.
During the two-year war at Zhongtiao Mountain, the Fourth Army had a long-standing tradition of cooperation with the Chinese Communists since Yang Hucheng founded the Ministry; on the other hand, it did not receive support from the Kuomintang side in terms of personnel and materials during the War of Resistance Against Japanese Aggression, but on the contrary, it received sincere help from all sides of the CPC's party, government, and army, and had close contacts with the CPC here. This naturally aroused Chiang Kai-shek's jealousy. Chiang Kai-shek transferred the Fourth Army away from Zhongtiao Mountain, in the name of the Defense Line of Henan garrisoning the south bank of the Yellow River for more than 100 miles, with the actual purpose of keeping the Fourth Army away from the Eighth Route Army of the Communist Party. General Sun Weiru was well aware of Chiang Kai-shek's intentions; on the one hand, he skillfully coped with Chiang Kai-shek's various conspiracies to persecute the troops by means of checking the "communist elements" in the troops; on the other hand, he carefully commanded the Fourth Army to carry out the Battle of Xing (Yang) Guang (Wu) and the Battle of Deng (Feng) (Shui), forcing the Japanese army to withdraw from Zhengzhou and besiege the qiaotou fort of Mount Yao. From the Battle of ZhongtiaoShan to the Battle of Henan, General Sun Weiru commanded the Fourth Army to rely on the help of the Chinese Communists and progressive people from all walks of life to stand out in the chaotic battle situation in which hundreds of thousands of well-equipped Kuomintang troops and the Japanese army were about to collapse at a touch, fled in the wind, and collapsed into an army.
In June 1945, Chiang Kai-shek saw that the japanese could not destroy this tenacious unit created by General Yang Hucheng, so he adopted the method of exchanging beams for beams, dropped away from the main generals of the Fourth Army, and sent his concubine General Zhang Yaoming to take over the troops. General Sun Weiru was transferred to Hubei as commander of the Sixth Theater of Operations, and Chiang Kai-shek stripped him of his military power by means of a bright rise and a dark surrender, placing him under the surveillance of his own forces. When Japan surrendered, Sun Weiru served as the commander of the Wuhan District surrender, actively responsible, disarming more than 200,000 Japanese troops, receiving more than 300 factories, warehouses, etc., and dispatching more than 90,000 puppet troops.