 Complete the following phrase:  The Su-34 had a murky and protracted beginning. In the mid-1980s, Sukhoi began developing a new tactical multirole combat aircraft to replace the swing-wing Su-24, which would incorporate a host of conflicting requirements. The bureau thus selected the Su-27, which excelled in maneuverability and range, and could carry a large payload, as the basis for the new fighter-bomber. More specifically, the aircraft was developed from , the naval trainer derivative of the Sukhoi Su-27K. The development, known internally as T-10V, was shelved at the end of the 1980s sharing the fate of the aircraft carrier Ulyanovsk; this was the result of the political upheaval in the Soviet Union and its 