Dude, you have no idea about the modern warfare. The only country Russia is actually afraid of is the USA. And nobody except probably the USA or maybe Turkey is even remotely ready for modern war. Russia is having "military operation" right now. If they start the "war".

Second of all, the "much smaller neighbour" is any European country to them. Ukraine is the biggest country on European continent if we include the occupied territory. And it's actually has the most capable armed forces military-wise. Russia took over 116k sq km of Ukraine. All three Baltic states are 175k sq km combined and they literally can't defend themselves in case USA decides to withdraw.

And last but not the least, Russia's war is irrational. It makes no sense from any rational viewpoint. So relying on common sense in this case is wrong. You need to understand russian ideology and Putin's specifically.