icebreaker, ship of special hull design and wide beam, with relatively flat bottom, designed to force its way through ice. When the icebreaker charges into the ice at full speed, its sharply inclined bow, meeting the edge of the ice, rises upon it, and the weight of the vessel causes the ice to collapse. A well-designed icebreaker is able to force its way through ice up to 35-ft (10.7-m) thick. In many northern seaports, especially in Russia, Canada, and the Great Lakes area of the United States, water-borne traffic in winter is only possible with the use of icebreakers. Icebreakers have been widely used in the exploration of the Arctic and the Antarctic. The first notable icebreaker was the Pilot (1870), used to maintain communication between Kronstadt and St. Petersburg. In 1959, the Soviet Union launched the first nuclear-powered icebreaker, the Lenin.