The Savage Mountains area, located on the border between China and Myanmar, the northernmost part of Myanmar, is an undeveloped primeval forest. Due to the dense forests and miasma in the mountains, the mountains are inhabited by some barbarian groups (mainly Kachin, and a few people whose ethnicity is difficult to determine), who live deep in the mountains and do not associate with modern civilized people, and are called "savages" by the locals. 
Back in the forties of the last century, in order to achieve the final victory of the Anti-Japanese War and ensure the smooth flow of the Yunnan-Burma Highway, the last transportation route between China and the world, more than 100,000 people from 9 divisions of the Chinese Expeditionary Force entered Burma to fight. After more than a month of heroic fighting, the Chinese Expeditionary Force was praised by the world for its bravery and tenacity in the battles to defend Tonggu and Ren'anqiang and rescue the British army. However, due to the late timing of the expedition, the lack of coordination of the Allied forces' operations, improper deployment, and multiple commands, the expeditionary force was always in a passive position and failed to achieve its initial campaign attempt. 
On May 9, 1942, Du Yuming saw that Myitkyina on the Yunnan-Burma Highway had been occupied by the Japanese army, and ordered all his troops to go northwest through the Savage Mountains and return to Yunnan. The large army led by Du Yuming did not suffer much losses in the battle with the Japanese army, but quickly fell into trouble in the Savage Mountain, and only more than 3,000 of the 35,000 people remained, what happened? 
A veteran of the Anti-Japanese War named Zheng Zixuan once recalled: "In Savage Mountain, the most terrifying thing is not the Japanese army, but the blood-sucking leeches and poisonous mosquitoes. Savage Mountain is high and densely forested, no matter how tightly you tie your boots, the strong leeches can also get in, and when you wake up, the leeches are swollen to death. Mosquitoes are very large there, and after being bitten by mosquitoes, you will get a fever. It's all poisonous mosquitoes! ”
In fact, as Zheng Zixuan said. The Chinese Expeditionary Force ran out of food in the Savage Mountains, the morale of the army was weakened, and diseases were epidemic. If a person falls unconscious due to high fever, he will be turned into white bones within a few hours by locusts sucking blood, ants eroding and heavy rain, and even the bones will be scattered all over the field, one after another, and the tragedy will be terrible. According to the data, among the 100,000 troops of the entire Chinese Expeditionary Force who entered Burma to participate in the war, more than 20,000 people died in the battle at that time, but more than 30,000 died in the Savage Mountain, and the cause of death was miasma and malaria brought by leeches and poisonous mosquitoes.