After the outbreak of the Pacific War, China formed an anti-fascist united front with the Soviet Union, the United States, Britain, Southeast Asia, and Oceania. In January of the same year, at the suggestion of the United States and Britain, the headquarters of the Chinese theater of operations (initially including China, Thailand, Vietnam, and northern Burma) was established, and in March, the Japanese army attacked Burma (then a British colony), and the British defenders were in a hurry. More than 100,000 Chinese troops, mainly the 5th, 6th, and 66th armies, formed the 1st Route of the Chinese Expeditionary Force, and under the command of Commander Luo Zhuoying, entered Burma to fight side by side with the allied forces.

On the 8th, the Japanese 15th Army landed in Rangoon under the command of Commander Shojiro Iida and marched north by separate routes. All the way, the 33rd Division attacked Beimiu along the east bank of the Irrawaddy River from Yangon, and the 55th Division attacked Donghu and Pyinbunna north from Bago to Yangman Railway in an attempt to cut off the international communication line in southwest China.

In March 1942 (the 31st year of the Republic of China), in the Sino-Japanese War, the Chinese Expeditionary Force conducted a defensive campaign against the Japanese 15th Army in the southwest of Yunnan Province, Burma, northwest Thailand and northeast India.

Li Ming, then chief of staff and commander-in-chief of the Sixth Army of the Chinese Expeditionary Force, heard that there were Japanese troops in the vicinity, and if he wanted to go to Burma, it seemed inevitable that he would exchange fire with the Japanese army.

The Chinese Army in India and the Chinese Expeditionary Force, in coordination with the United States and the British, attacked the Japanese Burma Front in northern Burma and western Yunnan Province.

In the spring of 1942, Japanese troops invaded Burma. At the request of the British army, China sent an expeditionary force into Burma to support the British army in the war. After the failure of the invasion of Burma (see Battle of Yunnan), the first part of the Chinese Expeditionary Force entered India and was organized as the Chinese Army in India. The other retreated to western Yunnan and expanded into two group armies. In March 1942, in order to implement the decision of the Allied Quebec Conference to launch an offensive against the Japanese army in Burma and open up the international communication line in southwest China, the troops stationed in India under the command of the commander-in-chief Stilwell successively assembled in the Ledo area on the Indo-Burmese border to prepare for an offensive against the Japanese army in northern Burma; Wei Lihuang, commander of the expeditionary force stationed in western Yunnan, decided to launch an attack on the Japanese army with Tengchong as the goal. The Japanese army stationed in northern Burma and on the west bank of the Nu River had a total of 4 divisions, 9 infantry wings and 8 special forces wings, and carried out defense under the command of the commander of the 33rd Army, Honda Masasai

The Sixth Army began to attack the Japanese army under the command of Li Ming, and the National Army quickly broke through the Japanese positions with the support of tanks and entered the jungle area of Burma, on March 15, the 80,000 troops of the National Army advanced all the way, and on the 14th, the new 38th Division of the Indian Army broke through the 18th Division of the Japanese Army, captured Xinpingyang, and entered northern Burma. In December, it attacked the New Beiyang Ocean and entered northern Burma.

The newly formed 38th and 22nd divisions captured Dabaijia and Tailuo respectively, and in early March, they captured Mengguan and Waruban. The Japanese army retreated to the Jebu Pass and resisted stubbornly. The new 22nd Division, in coordination with the new 38th Division and the 5307th Detachment (two battalions) of the U.S. Army, captured the 10-kilometer-long Jebu Pass after 14 days of fighting (see Mengguan Battle of the Jebu Pass). The remnants of the Japanese army retreated towards the Menggong River Valley. Subsequently, the 5307th Detachment and the newly formed 30th Division and the 50th Division, which had newly arrived in the Tekli area, were mixed into a Sino-American assault detachment and continued to advance towards Myitkyina; The newly formed 38th Division advanced towards Gaoli.

The Sixth Army was also advancing, and the weapons and ammunition were greatly consumed, but they were quickly replenished, and the Japanese troops who retreated to the Menggong River Valley were reinforced and held in Gaoli, Yingkaitang and Kameng. At the end of April, the new 22nd Division, with the cooperation of the new 38th Division, attacked the Japanese army, and after more than a month of hard fighting, all the above places were conquered on June 19. Then, the new 38th Division made a rapid advance towards Menggong, and the new 22nd Division made a detour to Menggong from the west (see Battle of Menggong River Valley).

At this time, the 20th Group Army of the Expeditionary Force crossed the Nu River from Lichaiba to Shuanghongqiao in western Yunnan, and after more than a month of fierce fighting, it conquered the Japanese strongholds such as Masian Pass, Hokusai Gongfang, and Jiangtho Street, and approached the periphery of Tengchong. The 11th Army also crossed the Nu River in support of the 20th Army. On May 22, in accordance with the telegram order of the National Military Commission on the rapid capture of Tengchong and Longling and the division of the army stationed in India in northern Burma and the opening of the Sino-Indian highway, the expeditionary force attacked Tengchong with the 20th Group Army as the right group, and the 11th Group Army as the left group to attack Longling and Mangshi. In early June, the 11th Army launched a full-scale offensive against the Japanese. The main force of the 71st Army crossed the Nu River and attacked Longling, and the fierce battle lasted until the 21st, and the two sides formed a standoff.

The main force of the 2nd Army crossed the Nu River, besieged Pingjia with one part, and attacked Longling with the 71st Army with the other. The 8th Army of the General Reserve of the Expeditionary Force crossed the river one by one in early June and joined the 71st Army in the attack on Longling. At the same time, the newly formed 38th Division attacked and annihilated the Japanese army in the northeast of Menggong, relieved the danger of the 36th Division of the British and Indian Army attacked by the Japanese army, and advanced to Menggong City; The newly formed 22nd Division connected the strongholds on the periphery of Menggong and surrounded Menggong City. After two days and nights of fighting, Menggong was conquered on the 25th. The remnants of the Japanese retreated in the direction of Myitkyina. Myitkyina, an important town in northern Burma, garrisoned two wings of the Japanese army. After more than two months of fierce fighting, the Indian army and the Sino-American mixed assault detachment that had arrived in the suburbs of the area launched an attack on the Japanese army, and on August 5, most of the Japanese troops were annihilated, and a few retreated to Bamo.

The 20th Army of the Expeditionary Force launched an attack on Tengchong, and the Japanese army resisted stubbornly and conquered Tengchong on September 14 after hard fighting, and all the Japanese troops were annihilated. On July 13, the 1L Army launched another attack on Longling, and with the support of the 20th Army, it captured Longling on November 6, and most of the Japanese army was annihilated, and a few retreated to Mangshi. After that, the 11th Army attacked Mangshi, Shafang, Wanmachi, and Mangyu. After conquering Myitkyina, the Indian garrison divided its troops into the new 1st Army (under the jurisdiction of the 38th and 30th Divisions) and the new 6th Army (under the jurisdiction of the 22nd, 14th, and 50th Divisions). On November 14, the new 38th Division arrived near Ba Mo, and with the cooperation of the new 22nd Division and the Air Force, after more than 20 days of fighting, it defeated a reinforced wing of the Japanese 2nd Division and captured Ba Mo. The new 30th Division conquered Nankan on January 15, 1945, most of the Japanese army was annihilated, and the remnants retreated to Lashio.

After taking over the task of the new 22nd Division near Mangka, the 50th Division attacked southward, breaking through the Japanese Division at Manhao and continuing to advance towards Maura . The 1st Division of the 36th Division of the Anglo-Indian Army advanced in the direction of Jomay. After conquering Nankan, the new 38th Division and the new 30th Division attacked in the direction of Mangyou and Laolong respectively. The newly formed 38th Division connected the remnants of the Japanese strongholds along the Yunnan-Burma Road (from Kunming to Lashio via Nankan), conquered Mangyou on the 27th, joined forces with the expeditionary force, and completely opened up the Sino-Indian Highway (a collective name for Kunming from Ledo to Kunming via Nankan). The 30th Division, with the support of the 1st Division of the 38th Division, after more than 50 days of fighting, conquered Lashio on 8 March (see Battle of New Lashio), continued to pursue to Khamsa, and joined up with the 1st Division of the 50th Division on the 27th. The other part of the 50th Division joined forces with the Anglo-Indian Army at Jomay. The remnants of the Japanese army retreated in the direction of Jingdong. At this point, the battle ended.

The campaign lasted seven months, and at the cost of 31,443 killed and 35,948 wounded, the Nationalist Army killed and wounded more than 25,000 Japanese soldiers, opening up the international communication line in southwest China.