The two-man Soviet crew, Anatoly Filipchenko and Nikolai Rukavishnikov, tested a docking ring and other systems to be used in the joint flight.

[4] The Soviet Union and the United States, Cold War rivals, had signed several arms control treaties in the 1960s and 1970s, and had entered into a period of detente by the early 1970s.

Once the Americans abandoned their Skylab station in 1974, the Apollo-Salyut concept seemed to be the logical choice, but since the Soviets had started to develop a universal docking adapter for the mission and feared having to publicly reveal details of their military-focused Salyut missions, the two powers opted to link a Soyuz spacecraft with an Apollo spacecraft.

NASA officials refused to agree to that condition and, accordingly, were informed of the launch an hour after it occurred, on 2 December 1974.

[5] On 7 December 1974, the docking ring was jettisoned with explosive bolts to test emergency measures if the capture latches got stuck during the ASTP flight.