There were four M41 tanks used in the film and they were all operated by the Belgian army with real training ammo (as opposed to fireworks in the barrels or mock-up tanks). A Belgian Army colonel admired Kubrick’s earlier works and lent him the tanks.

This entire scene is like a sociopathic masterclass on damage control.

Thus Spoke Zarathustra is a book for "All and None" by the German philosopher Friedrich Nietzsche where the prophet Zarathustra proclaims to the world that God is Dead. "Also sprach Zarathustra" is a tone poem by Richard Strauss - the song. What is happening to the "ape" (when human consciousness is first formed and their first act is to make a weapon and kill each other) speaks more to the book. Zarathustra states, "Man is a rope stretched between the animal and the Overman." This is our beginning, "we" are in the middle of evolution and the "ubermensch" is the end. from the book: "You have evolved from worm to man, but much within you is still worm. Once you were apes, yet even now man is more of an ape than any of the apes." "What is great in man is that he is a bridge and not a goal: what is lovable in man is that he is an over-going and a down-going." A Space Odyssey is a Nietzschean film. During World War 1 most German soldiers heading to the trenches had a copy of the Bible in one pocket and this book in the other.

Nicholson hits the door three times. With each swing, the camera follows the movement perfectly, then stops abruptly with every impact—as if it were striking the door too. The slight shake and hard stop give each blow its power while creating a real separation between Jack and Wendy’s two spaces.

When the voice changes to the raspy, high-pitched tone is what makes the scene the most uncanny to me. The change from his normal voice actually makes it seems like there is some supernatural force controlling his voice and body.

Kubrick would not approve of this editing. In the real scene it's very creepy. It almost drags on, why? Because Hal is THINKING.

I'll be honest - I've always found this moment to be hysterically funny. And why is it people can't see that the bloke has a deep gash down the skull, not just blood on him?