This song is about man's desire to kill and destroy. Sabbath got the idea from war stories they heard when they did a show at an American Air Force base during a tour of Europe. They wrote the song when they were in a grim deserted place in Zurich where they were playing for a small sum of money to an even smaller audience.
The band wanted to use this as the title of the album, but the record company thought it was too controversial and made them use "Paranoid," another song on the album, instead.
This is one of many Black Sabbath songs that is often misinterpreted as evil. The song speaks out against the horrors of war.
The song was inspired by the Vietnam War. Geezer Butler recalled to Mojo in 2017: "Britain was on the verge of being brought into it, there was protests in the street, all kinds of anti -Vietnam things going on. War is the real Satanism. Politicians are the real Satanists. That's what I was trying to say."