There's always a bigger fish.
The last time nations were obsessed with autarky, we got WW1, and soon after, WW2.
Most countries (i.e. every country not suffering from a drastic case of the resource curse) have the nature that if they trade a lot with another country, either country would lose economic value if they invade the other, _even if_ that invasion goes off stellarly well with almost no losses: The populace doesn't like being subjugated and produces significantly less.
In an inbalanced trade/dependency relationship, such as Saudi Arabia's oil vs. the rest of the world, or Russia's gas vs. europe, it's actually _both_ sides that are dependent on the other. It's the dutch curse all over again.
Go back in time:
* Europe wants more gas to grow its economy, and doesn't have enough on its own soil. * Russia has more than plenty and is willing to sell it. * We enter a period of years where europe companies and countries more and more build industry that isn't going to work out without the relatively cheap russian gas. As these industries continue to succeed and russia continues to be a reliable supplier, ever more industry takes the leap and becomes dependent on it. * This sounds like handing off quite the 'weapon' to your supplier, but, the problem is, that supplier is now just as dependent on this relationship as the consumer is: Russian economy falls apart without the trade of europe-produced goods (a lot of it by industries that run on russian gas), just as fast as europe falls apart without russian gas.
Thus, if russia were to invade europe, russia's economic value falls off a cliff, and the same applies to a lesser extent to europe. The only reason europe could in theory invade russia (assumes a perfect invasion, no nukes, no significant resistance at all, just a dejected populace), is because russia's primary value is not particularly dependent on human capital.
My theory about why this theory didn't work out and russia invades ukraine is a mix of:
* Misunderstanding by Russia of world/Europe response to this invasion. * Too much power in one person, who, like most people surrounded by yay-sayers for 20 years, has lost grip on reality. * Most of all, a ticking clock: Europe has stated they want to wean themselves off of fossil fuel within a decade or so. And so they should, but it's a torpedo to the trade dependency relationship between europe and russia.
That last one is the economic argument: Russia had to do something or their economy would fall apart if europe delivers on their plans to rapidly reduce their dependence on (russian-supplied) gas.
Thus, autarky -> war. Because if you're doing economically better than your neighbouring country, you produce more weapons and more people, and just invade em, why not.
We can trade the risk of what happened to europe, or what is likely to happen if china and the west become autarkic relative to each other (namely, that china invades taiwan) - with nukes and MAD. But that's got its own problems.