I have some military ranks used in my dialogue such as: “What did you see, Private?” he asked. “Couldn’t tell, sir. It wasn’t human, I can say that much,” Private Eun said. “Right away, sir,” confirmed the private. However, I'm not entirely sure as to whether I always capitalise the rank or only when used with a name. For example: "What did you see, private?" he asked. "Couldn't tell, sir, I can say that much," Private Eun said. "Right away, sir," confirmed the private. Can someone enlighten me on this?