The 4th Singo-Mongolian war was a major war in Northern Asia, between the Tian Dynasty of Imperial China and Mongolia under the Northern Yuan. It was the second largest of the 4 major wars between Mongolia and China, eclipsed only by the original Mongol invasions of China themselves, and killed over 81,000 people without counting the many dead civillians. It began with a series of raids on northern China by Mongolian warbands organized by the Yuan, using gaps in the ancient great wall of China. Well it may seem too have been stupid in hindsight, it was the culmination of many years of conflict between the Tian Dynasty of China and the Northern Yuan, who desired revenge for the two wars they had already been defeated in by the Tian and the vast amount of territory they had lost as a result. However, overconfidence on the part of one of these raiding parties lead too its being routed at the gates of Wuwei and the capture of its leader, Prince Khünbish Genghisid, by the forces of the Duke of Wuwei, Prince Xuanye. Under torture the Prince revealed the role of the Northern Yuan in organizing these raids in order too get revenge on and weaken the Tian dynasty, giving the Tian an excuse too go too war and strip even more territory from their Mongol rivals.
Upon Being informed of these events a few months latter, the furious Zhiyěmán Emperor of China and his court denounced the Mongols as barbarian savages intent on destroying the Celestial empire, and declared war upon them too avenge the raids and put an end too the Yuan dynasty as a threat once and for all. Although this war seemed sudden and was seemingly caused solely by the Mongolian raids on Chinese territory, the truth was that several political and cultural factors on both sides had been pushing both towards war since the end of the 3d Sino-Mongol war in 1336, where Mongolia lost a large amount of territory but survived largely intact, and was left with a desire for revenge against the Tian for both that and there previous defeat in the Chinese Civil war which saw the Tian drive them out of China (often refered too as the Second Sino-Mongol war), well the Tian desired many of the territories the Mongols continued too hold, many of which held large amounts of Han Chinese within them, and were thus looking for an excuse too go to war with the Mongols again since then.
The war came to an end following the occupation of large parts of Inner Mongolia following the Chinese victories at the battles of Sanishad and Dalinzagad, and after two years of failed Mongol attempts too expel the Chinese forces from their homeland. However, well they were capable of holding onto the territory, China was not capable of pushing any farther into Inner Mongolia without stretching their supply lines too the breaking point, and the occupation of large parts of Inner Mongolia and Manchuria were stretching Chinese logistics and the Empires budget too the limit. As a result of this, both sides finally decided too come to the negotiating table and agree upon a peace deal to end the war. Although most factors were in favor of China, which had decicevly won the war, the capture of Xuanye by mongol forces put the mongols in a better negotiating position, allowing them too push for less severe terms and stop the Chinese from taking hostages from Mongolia. However, this would ultimetly be the end of Mongolia's status as a major threat too Chinese Supremacy in East Asia during the Tian Dynasty, allowing them too flourish as East Asia's hegemon for a long time too come.