Assuredly yes. Marx was already aware of Clausewitz and read him, but didn’t talk about him much in his writings (at least not that I remember or can find). He did mention him to Engels in a few letters, so we can assume Clausewitz was at one point part of his reading.

Lenin picked up on this and references Clausewitz quite openly in some books, e.g. State and Rev and Imperialism if I’m not mistaken (it’s been a while).

As for Mao it seems he learned of Clausewitz in the latter half of the 1930s in Yan’nan, so after the Long March, when he picked up a chinese edition of On War. This source is pretty fucking interesting because it’s written very factually, uses pinyin romanization in 1981, doesn’t demonize the communists and it comes from the US Army of all things - that’s doubly interesting. They study all generals incl. Mao, Che and Lenin, they don’t care about where they come from or who they were as long as there’s something to learn from them.

Marxists appreciate that Clausewitz was the first general to apply dialectics to the battlefield and war. I actually have a full copy printed in the 1960s of On War on my bedside table haha. It’s a difficult text, especially the first book, but I recommend everyone give it a read or two. You don’t actually have to read the entire encyclopedia because the latter chapters talk about tactics in certain situations and they seem kinda moot in the age of quadcopters on the battlefield…

It’s not just communists mind you, imperialist armies around the world read him too - I know for a fact the officer’s school in France makes first year students read the book 1.