It’s true that Russian Empire (not the USSR) invaded and annexed a load of territory but I have no clue how many square km it is. Did not bother to count.
Most significant losses are the Outer Manchurian homeland of the Qing Dynasty, including Sakhalin Island, whose very name is derived from Manchurian. The major settlement was Haishenwei (海參威), now called Vladivostok. The Chinese that lived in those lands were expelled brutally. One story claimed that a village of 5000 people near present day Khabarovsk was driven to the raging freezing cold Amur River (黑龍江) at gun point, and told to cross it or be shot. In other words, they were fucked…
All the grey areas are lost territories of China between 1840 and 1911.
What is not shown here is that Tuva (Tannu Uriankhai 唐努烏梁海) and Outer Mongolia were also eventually invaded and occupied by the Russians, resulting in the present day map of China, PRC.
I am very familiar with these lost territories because I have a souvenir map of China from a Taiwanese friend, whose government formally claims all the land that China inherited in 1911.
Xinjiang (Sinkiang 新疆) was also going to be lost to Russia, which supported the East Turkistan independence movement, but Mao and Stalin made a deal and it remained in Chinese hands.
Now you know why is China not supporting Russia over the Russia-Ukraine Crimea conflict.
And as for “never going to return”, well that also is complicated. On one hand, China had reversed its unequal treaties with everyone, except Russia. On the other hand, Mao and the CCP owe their VERY EXISTENCE to the USSR, first for saving their asses after the Long March and then airlifting them to Manchuria immediately after WWII in violation to the agreement with the ROC. So when the PRC was founded, Soviet puppet Mongolia was recognized and the rest of the lost territories were not mentioned again, because Stalin and Mao were BFFs.
Then Stalin died. And his successor Khrushchev had a fall out with Mao, cumulating to the Sino Soviet Split of the 1960s. NOW, Mao raises the Russian imperialism issues, and obviously Khrushchev was like LOL … no go away. Grievances eventually exploded into the Sino Soviet border clashes. Miraculously, two nuclear powers ready to punch each other’s lights out did not go nuclear, to the somewhat disappointment of Kissinger.
Geopolitics have made Russia and China dependent on each other and neither can afford another potential issue in the future. In 2002(?), Russia and China settled their borders, resulting in Russia giving away some islands (i forget which ones). This pissed off the Russian people, especially those who lived on or near the islands. This pissed off the Chinese people, who genuinely believed that those lands were Chinese and the issue should be left open for future discussion. My reaction to the news was “c’mon Russia, you already took a shit load of land already, just give us back a few damn islands and stop bitching.” But you know it’s a good deal when no one is happy with the results :P
THIS is probably where the “never going to return” part comes from. And barring a total collapse of the Russian Federation and with the blessing of the United States, China is never getting these lands back.
This is also why Russia is very wary of Chinese people even just simply living in the Russian Far East. A friend from Russia also says her school curriculum never mentioned Russia’s Far East history at all… as if Vladivostok just landed out of nowhere on Russian land.
Dear Russian friends: I assure you that China has no intention of taking back these lands, as it is much better for China to trade with Russia, who has already invested in the infrastructures for extracting and transporting resources. War is bad for business, and China is all about business :)
And what did China learn from all this?
Might is right: it doesn’t matter what you say, if you don’t have the force to back it up, any claim is empty.
Use it or lose it: the Russians quite literally walked into Manchuria and stayed there. If China had more population in Outer Manchuria, it would have been a lot more difficult for Russia to annex it.
So is there any surprise why China is now is so “assertive” in military and economic developments regarding its legitimate historical claims in the South and East China Seas?