At 19.54 hours on 31 Jan, 1940, the unescorted Vidar was hit aft by a G7e torpedo from U-21 about 100 miles east of the Moray Firth and sank the next day. At 19.48 hours, the U-boat had fired a G7a torpedo that became a surface runner and detonated near the ship, which stopped. A second torpedo had been fired two minutes later, but did not run due to an operating error. The Danish steam merchant Disko, which picked up the survivors from Vidar, was attacked with a G7e torpedo at 20.11 hours, but it also became a surface runner that detonated without damaging the ship.