In the mid-1950s, the Soviet Union began developing a new diesel-electric icebreaker design based on the 1942-built steam-powered icebreaker Eisbär to meet the needs of both civilian and naval operators. Built in various configurations until the early 1980s, the Project 97 icebreakers and their derivatives became the largest and longest-running class of icebreakers and icebreaking vessels built in the world. Of the 32 ships built in total, the unarmed civilian variant Project 97A was the most numerous with twelve icebreakers built in 1961–1971.[3]
Project 97A icebreakers were 67.7 metres (222 ft) long overall and had a beam of 18 metres (59 ft). Fully laden, the vessels drew 5.35 metres (17.6 ft) of water and had a displacement of 2,935 tonnes (2,889 long tons). Their three 1,800-horsepower (1,300 kW) 10-cylinder 13D100 two-strokeopposed-pistondiesel engines were coupled to generators that powered electric propulsion motors driving two propellers in the stern and a third one in the bow. Project 97A icebreakers were capable of breaking 70 to 75 centimetres (28 to 30 in) thick snow-covered ice at very slow but continuous speed.[3]