Nearly every time Russia has been invaded, it has been saved by its strategic depth. Russia can’t truly be defeated without first taking Moscow, and it is a long way to Moscow. From Napoleon to Hitler, invaders from the west had to try to reach the capital city before the brutal winter came – indeed, it helped to arrive before the rains of autumn choked the roads with mud. Russia must therefore keep the starting point of an attack as far away as possible and use its army to delay its advance as much as possible.
Thus is the strategic value of Ukraine to Russia. If Ukraine remains intact, and if it becomes a part of NATO, Moscow would be less than 300 miles (480 kilometers) from the attackers. Many argue that NATO has no intention of invading. I argue that nothing is less reliable than intentions. War planners must plan on capabilities, which are much slower to change than intentions. Considerations such as the rights of sovereign nations have historically always taken a back seat to the need to guarantee the security of a nation.