During World War II, some people wanted to disrupt or stop the trains from delivering supplies to enemy soldiers. They did this by doing bad things to the train tracks, like breaking them or putting things on them to make the trains crash. They also sometimes put bombs on the trains to destroy them. This made it very hard for the soldiers to get the things they needed, and it made the war more difficult. It was a bad thing to do because it hurt many people, even some who were not involved in the war.