Predecessors: T-55 and TR-580
After the Warsaw Pact invasion of Czechoslovakia, Communist Romania adopted a new national defense doctrine. However, this new doctrine required a self-sustainable local defense industry. In April 1968 a preliminary report regarding the production of tanks in Romania was proposed to the National Defense Council of Romania. The report was ratified by the Defense Council on the 13th of October 1972. The development of a Romanian medium tank effectively started on the 13th of May 1974. The Romanian Defense Council wrote the specifications for the medium tank. The new vehicle would have a weight of approximately 40 tons, a 100 mm main gun and a 500 horse power engine.
The next step taken was the production of 400 derivatives of the T-55 tank, as the local arms industry lacked the experience required to design and produce a medium tank from scratch. The Communist government did not buy the license for the T-55 tank. The initial batch (the prototype and the first 10 tanks), officially known as the TR-77 tank (Tanc românesc model 1977 Romanian Tank model 1977), was intended to use the Leopard 1 engine and, as a result, the hull was extended, having 6 instead of the usual 5 road wheels of the T-55 tank.
However, because of the political need to reach the established production figures and the refusal of Krauss-Maffei to deliver technology to a Warsaw Pact member, the medium tank, known as the TR-77-580 (Tanc Românesc model 1977 cu motor de 580 cp Romanian Tank with 580 hp engine), was built using the V-55 engine of the T-55 tank and the extended chassis. The TR-77 tank was developed between 1974 and 1980 and was produced between 1979 and 1985.
Read more about this topic: TR-85