The one genre Kubrick has dabbled in a couple of times is the 'war' genre - with both Full Metal Jacket and Paths of Glory. You could argue that Spartacus has a war-like element to it. The thing is with Full Metal Jacket is how it also delves into the psychology of war too.
Many moons ago, I wrote a little review about the film writing:
"On his head is a symbol or peace and, next to it, the words "born to kill". This complete conflict, two polar-opposite attitudes to war, is what roots itself in the themes of this film - these two stances are what makes men so conflicting in their stance towards war and violence. They can make a man go mad."
Its an incredible film, and the full write-up goes into much more depth - so if you want to read more - click here