In 1956, I was OOD and had the conn during the midwatch when a large merchant was approaching from astern a slight angle starboard. Watching the slow approach on our old surface radar which indicated it to be on collision course, I finally called the Captain (CDR Bailey) to the bridge. As we were the ‘Privileged Vessel’, we were hoping the ‘burdened’ merchie would slow or veer off but she continued on. As she got closer we blasted on the horn and flashed spotlights up to her bridge as well as calling on the radio, all to no avail. Assuming “in the jaws of collision”, we eased to port so she’d pass us on a parallel course, which is what safely happened. We assumed she was on autopilot with no one on the bridge.