Ulk

Ulk was a nation on the planet Int which was at war with Gor. At one point during the war, the people of Ulk launched a boat carrying a powerful bomb towards Gor, but the First Doctor, John and Gillian arrived on board. They discovered the danger and attempted to leave, but interference from the boat's force field prevented the TARDIS from dematerialising. The Doctor cut down one of the boat's masts and used it as an oar to steer the boat onto a course back to Ulk. To save themselves, the people of Ulk deactivated the force field so missiles fired from Gor would destroy it, but not before the time travellers departed. (COMIC: Deadly Vessel)