Bret Devereaux over at A Collection of Unmitigated pedantry did an overview of the modern theory of protracted war / i.e. how to win a war if you're the weaker party: https://acoup.blog/2022/03/03/collections-how-the-weak-can-win-a-primer-on-protracted-war/
I'm sure some folks here are well versed in the subject (and if so, please point out flaws or develop his argument further), but I found it interesting nonetheless.
It helped me crystalize a question that's I've been trying to get a sense of: at what speed and at what level of impact can we expect the current level of sanctions to degrade Russia's ability to wage war?