The Diaoyu City defender Wang Jian prevented the Mongols from the third western expedition and indirectly saved Europe, the following is the background and explanation.

Why are Europeans so wary of the Orientals and have a "yellow peril"?
As we all know, in the era of cold weapons before guns appeared, the Mongolian Iron Horse was the most powerful army in the world.
After Genghis Khan unified the Mongol departments, he began a war of foreign expansion, and Mongolia launched three large-scale western expeditions, the first of which was genghis Khan personally led a large army to conquer the Central Asian countries and destroyed the Khwarazm State, one of the most powerful empires in the world at that time.
After the death of Genghis Khan, his son Wokoutai launched the second western expedition, the Mongol Iron Horse successively conquered the Russian princely states, and then killed the Polish and Germanic allies to the danube, all the way to the Danube River, the whole of Europe was trembling with fear, thinking that God punished the Europeans, calling the Mongol army "God's whip"! The expedition ended with the death of Wokoutai.
Genghis Khan's grandson Möngke succeeded to the throne and launched the Third Western Expedition.
We have to understand that the policy adopted by the Mongols at that time was to slaughter the city after the siege, often hundreds of thousands of people1. During the attack on Diaoyu City, the general Wang Jian struggled to resist and take advantage of the geographical advantages, fighting with the Mongols for more than 30 years, and finally Möngke died in the war. The Mongols changed their policy and did not slaughter the city.
Diaoyu City is well located
Wang Jian insisted on holding on to diaoyu City, bringing time for Recuperation to Europe, and also allowing the Mongols to change their attack and choose to establish a state in the land of China and become emperor.
The Battle of Diaoyu City is also referred to by some Western scholars as "God's Whiplash.". Central Asian scholars also refer to diaoyu city as the "Jerusalem of the East."
European civilization is nothing remarkable, it used to catch up with us, and now we also have the confidence to walk alone in the world!