On May 21, 1935, the advance troops of the Red Army entered the Yi District. Many Yi compatriots heard that the Red Army was an army of benevolence and righteousness, but they were still dubious. Seeing this Han-dominated army entering their control area, many Yi people gathered around with steel guns, earthen guns, and bows and arrows. They shouted slogans that the Han people could not understand, occupied mountain passes and blocked the way.

Liu Bocheng, Nie Rongzhen and others ordered that they should not shoot when encountering obstruction or robbery by Yi people, but could only persuade and explain. When the advance troops passed the Ewa Pass, a group of Yi armed forces suddenly rushed down, attacked the engineering company walking behind the troops, and stripped off their clothes. The commanders and fighters of this company strictly obeyed the order and did not resist. As a result, they ran back naked and in tears.

The Red Army had no choice but to shorten its marching distance, enforce strict military discipline, and adopt an attitude of ignoring the invasion and not fighting back. The Yi people, who had just been liberated from Mianning Prison, walked in front of the Red Army team and acted as translators, explaining that the Red Army was just using the road to go north this time and would never be enemies of the Yi people. At this time, Xiao Yedan, the leader of the Guyi branch, sent his fourth uncle and Shamar, who was proficient in Chinese, to Lama Fang Jiang's store to inquire about the situation, and learned that the Red Army was indeed different from the Kuomintang army seen before. When the two sides faced off, Xiao Yedan rushed to the front on horseback. The Red Army noticed that this man's attire was unusual and called him through an interpreter. The answer he received was that he agreed to talk.

Xiao Yedan first sat on the ground with Xiao Hua, the captain of the Red Army’s mass work team, and had a conversation, and learned that the Red Army just wanted to use the road to pass. He saw that the Red Army rescued the Yi people imprisoned by the Kuomintang and had strict discipline. Based on the traditional concept of "the more friends the better, the fewer enemies the better", he agreed to make friends. At this time, the two Yi tribes on the way forward of the Red Army - "Guji" and "Luohong" were constantly fighting with each other. As the leader of the "Guji" family, Xiao Yedan proposed to form an alliance with the Red Army and also wanted to use the power of the Red Army to defeat them. "Luohong" tribe. The Red Army was willing to form an alliance to reduce resistance on its way north and did not want to intervene in the internal conflicts of the Yi people. When Xiao Yedan proposed to become brothers with Commander Liu Bocheng of the Red Army advance team, Xiao Hua immediately went back to report. In order to unite the Yi compatriots and ensure the smooth passage of the main force, Liu Bocheng decided to play the leading role in this alliance.

On May 22, at the bank of Yihai Lake, more than 20 kilometers north of Mianning County, members of the Red Army advance team and many Yi compatriots attended the ceremony. Liu Bocheng and Xiaoye Dan took a blood oath and became brothers. Xiao Yedan also brought a rooster and slaughtered it by the lake. The two drank chicken blood wine and swore an oath to heaven. After the ceremony was completed, Liu Bocheng gave the revolver and some rifles he carried to Xiao Yedan, and Xiao Yedan also gave his mount to Liu Bocheng as a souvenir.

That night, Liu Bocheng held a banquet in honor of Xiao Yedan's uncle and nephew and his party at the camp bridge. In response to Xiao Yedan's idea of ????getting foreign aid to fight against enemies, Liu Bocheng suggested that the Yi people should unite within themselves, not fight enemies, but make peace; the Han and Yi people are one family, there should be no barriers, and they should work together to deal with the warlord Liu Wenhui. Later, Liu Bocheng awarded Xiao Yedan a team flag with the words "Guji Detachment of the Chinese Yimin Red Army" and appointed him as the detachment leader.

After the "Yihai Alliance", Xiao Yedan considered that other clans might still attack the Red Army, so he personally escorted him to the lama's room, and then sent his subordinates Guoji Nipo, Guoji Zida and Shamar to attack the Red Army. Others escorted him to Chaluo. Since the Red Army did not commit any crimes when they passed through the Yi area, and they had just rescued the imprisoned people of various tribes, other clans were also moved and did not attack the Red Army. In order to gain time and prevent accidents, the Red Army marched forcefully and passed through the Yi District within three days. When the commanders and soldiers marched quickly, the Yi compatriots on the roadside cheered, and there was a moving scene of "brothers and nations greeting each other on the road" sung in the song.