Am I the only one thinking that Russia would, if it truly had even the slightest understanding of what the long term means, realize that it is neither NATO nor Ukraine generally, nor the USA specifically, that is Russia's utterly natural enemy; rather, it is China. The two greatest expansionists in world history - far greater than even the Roman Empire - and they share one of the world's longest borders.
China is nothing if not a long-term player. The and their predecessor "Chinese" regimes and empires span from almost the earliest Nile River civilizatons to today - and in the succeeding millennia have incrementally grown from a small river-bound state to their present size. Russia has done likewise from a far later starting point, and now, they are head to head.
Here, courtesty of wikisomething, is one reckoning of longest shared borders. Include or omit Mongolia as you will:
- Canada-USA : 8,893 km.
- Russia-Kazakhstan : 6,846 km.
- Argentina-Chile : 5,300 km.
- Mongolia-China : 4,677 km.
- India-Bangladesh : 4,053 km.
- Russia-China : 3,645 km.
- Russia-Mongolia : 3,543 km.