The Zhukov Academy for Military Theory

von Clausewitz was a liberal and a bourgeois living in the 18th century, and yet his defining work, On War, is still relevant today.

Notably, he shows a certain dialectical thinking that was not seen by his contemporaries at the time. It's no surprise then that Lenin and Mao were acquainted with his work and cited him -- you may heave heard "War is only a continuation of State policy by other means" (or in different terms). This is straight from Clausewitz. He also explains that war will grow in scope as it goes on, as either forces will commit only as few resources as possible in the early stages, hoping for early victory, but will have to increase their efforts if the conflict goes on.

His book is very, very dense. I own a physical copy and it's more than 1000 pages of text in a format slightly smaller than standard paper. He also doesn't write in the most accessible manner, and he died before he could complete his work -- so probably some editing would have been done.

Not only does Clausewitz present the aspect of actual war -- how to attack certain positions but how to defend them as well, he talks about the theoretical aspect of war at length.

This book is still required reading in officer academies today (to some extent, they don't necessarily read all chapters) and any comrade who wishes to learn about warfare will have to go through it.

If anything I recommend reading the first book if you're not going to read the rest.