People are going to laugh at this, but it seems to me that Russia should be more concerned about China. China wants oil, timber, and farm land and what country has it all right next door, and has no allies who would come to its aid? Last century the USSR and Nazi Germany were sort-of-allies for a while, then Germany decided it wanted land and resources from the USSR and +30 million died in the next few years sorting that out.
Sure, the Russians are far better soldiers and would slaughter a lot of Chinese in the process, but what does China care? China has 10X the population as Russia, and China might actually be interested in the prospect of getting rid of a hundred million excess peasants in the process.
If China invades the Republic of China, the humaniatarian crisis on display in that densely populated country could push most of the world into containing China, crashing the Chinese economy and resulting in revolution. But if China contrives an excuse to invade Siberia, who would complain about it? In sparsely populated areas, the casualties are soliders, not civilians, and people care less for soldiers than for civilians. "Russia is always invading a neighbor, so now it is their turn--what goes around comes around." There were border skirmishes between the two countries in the 1960's if memory serves. It seems the only thing keeping the Chinese from rolling over half of Russia is the prospect of nuclear warheads landing in Beijing. The calculation may be how much land Russia would be willing to lose before triggering a mutually-assured-destruction nuclear exchange with China.
This is a pretty bad misread of the current (and even future) geopolitical situation in Eurasia/East Asia. Let me simplify things for you:
1- The people running western governments have an age-old hatred for Christian Slavs, developed over centuries of their Khazarian ancestors living in the Pale of the Settlement. Putin's revival of a strong nationalist, Christian Russian identity is a complete deal breaker for the ruling class in the US, Canada, UK or France. That's the main reason for the demonization of Russia and the long smear campaign against Putin.
The goal of Atlantist strategists, as outlined by Brzezinsky in his book The Grand Chessboard, a geopolitical bible of sorts in the US, is to break and dissolve Russia into 4-5 pieces, with the western part absorbed into the neoliberal western order like Ukraine, and its vast resources subjugated like those of an African economic colony (exactly what happened in 1990s Russia under Yeltsin).
Putin likes the West, and sees his country as a European nation. He was stationed in Germany as an analyst and is an admirer of German culture and philosophy. He kept making overtures that have been rebuffed, and is finally coming to understand that Russia will never be accepted as a strong independent nation by the West.
2- China's honeymoon in the West has ended. China is challenging the dollar-based New World Order, and is the biggest threat to the Fed financial system. It's an existential threat to the NWO. The real US debt is close to $40-$50 trillion, but has always been a meaningless figure with the US$ being the world fiat currency. This status supports the near bottomless printing of US$ and debt. If that were to change, the US would have to completely restructure its economy and would no longer be able to run massive deficits.
Thus China and the US are on a collision course, not necessarily from the perspective of the people of those countries, but definitely so from the perspective of western oligarchs.
This is why Russia and China now have a very strong alliance. The two countries are also highly complementary with Russia being a resource and military tech supoerpower, and China being an economic juggernaut and the world's leading market and consumer of resources.
Trump could have uncoupled that partnership through openings to Russia, but the Deep State made it clear that this would be out of the question.
Also, the idea of China coveting Siberia for its lebensraum is naive. China's population is set to decline by 500+ million this century, due to the one child policy they've had for 40+ years. Their focus is on maintaining their borders and integrating Taiwan.
If China wanted to expand beyond its borders, it would have no problem taking over Mongolia, which is a huge country, or maybe splitting Mongolia with Russia. This is a country and people a quarter the size of continental US with a population smaller than that of metro Seattle, and a country with a very long and continious history of invading both China and Russia, so from a historian nationalist perspecitive, it would be a somewhat justifiable payback... Mongolia is completely landlocked between Russia and China, it would be conquered in a weekend by China.
I don't think a Chinese plan to invade Mongolia is in the works, but the point here is that it would be the low-hanging fruit for any expansion plans beyond the Chinese areas of Taiwan/HK.