On March 24, 1914, the authorities of country Y and the local government of XZ secretly exchanged letters in Delhi, in which Henry McMahon, the foreign minister of Y was the foreign minister of Yd, concocted a boundary line between China and YD, the so-called "McMahon Line", which roughly follows the watershed of the Himalayas The traditional customary line of more than 90,000 square kilometers of Chinese territory in the north was included in the territory of Y, but the successive Chinese governments have never recognized this, so the Y side has not dared to control the zhì according to this line for a long time. In 1951, YD forces advanced north across the traditional customary line and occupied 90,000 square kilometers of Chinese territory south of the illegal "McMahon Line." Thereafter, the YD Army occupied the areas of Kanzemani north of the "McMahon Line" in the eastern sector, Juwa, Qujak, Shibuchi Pass, Borin Sando, Shanza and Labudei, and Baris in the central and western sectors. Later, the YD government openly made unreasonable demands to Huaxia to use the McMahon Line as the boundary, but after the Huaxia government refused, it pursued a "forward policy" and continued to encroach on Huaxia's territory.

In August and October 1959, the YD army caused the Langjiu and Kongkashankou incidents in the eastern and western sections of the border between China and YD, killing and wounding many officers and men of the Huaxia Border Guards. From 1961 and especially in April 1962, the YD army wantonly encroached on the territory of China; on September 20, 1962, the YD army crossed the "McMahon Line" in the eastern sector and launched an attack on the Huaxia border guards in the Kejielang area, and on October 10, attacked the Huaxia Chidong outpost in the eastern sector. On October 20, the YD army launched a large-scale attack on Huaxia, and in the face of the rampant aggression of the YD army, the Huaxia government could not bear it, and the Central Military Commission decided to carry out a self-defense counterattack operation. In the eastern sector, the Huaxia border troops advanced to the south of the "McMahon Line" near the traditional customary line, and in the western section, cleared all the strongholds of the Yin Army in Huaxia. On November 21, the Huaxia government issued a statement announcing a ceasefire and withdrawal of the Huaxia border troops along the entire Huaxia and Yindu borders. From December 1 to March 1, 1963, they withdrew to an area 20 kilometers north of the Huaxia side of the line actually controlled by the two sides on November 7, 1959, and released all 3,312 captured personnel under Brigadier General Ji Pu Dalvi, commander of the 7th Brigade of the Y Army, before May 26, 1963, and returned all captured weapons and equipment and military supplies.

Based on the principle of friendship between the two countries, the Chinese government has proposed an unconditional solution to the border issue between the two countries countless times over the past few decades, but it has always been rejected by the Y government, and therefore the border issue between the two countries remains unresolved to this day. In 1987, the Y government established the so-called 'Arunachal Pradesh' on the territory of China south of the illegal "McMahon Line".