The Soviets tried for a manned circumlunar mission carrying one
cosmonaut for round the moon flight to beat the US.
en.wikipedia.org...
Called ZOND (Probe) consisted of modified Soyuz capsule - using only
2 of the 3 modules, the re-entry module containing the heat shield and
parachutes, the service module with the solar panels, batteries and maneuvering engines/thrusters. Deleted was the orbital module where
crew would live/work while in space.
The Zond used a "double dip" re-entry maneuver to reduce heat and
aerodynamic stress on the system.
The capsule would begin re-entry over the south pole and skip back 400
miles into space where it then do a normal re-entry as gravity pulled it back.
Boosted by D class (Proton) booster could fly Figure 8 trajectory around
moon and back to earth.
en.wikipedia.org...(rocket)
The idea was to beat the US to the moon and score a propoganda victory
Numerous Zond missions were lauched through 1967-69, experiencing many failures with the rocket booster. Other mission which successfully
made the moon journey only to experience failure on re-entry or in
other systems - failure which would have killed any human passenger.
The Apollo 8 mission was result of the Zond missions - NASA and US government officials were concerned that the Soviets pull off another
propoganda mission upstaging Apollo. In Mid 1968 US had Saturn V
launch booster ready, sucess of Apollo 7 (Sept 1968) had proved out
hardware. Lunar Module redesign was still lagging - NASA said what the
hell, just take shot at moon to prevent Soviets from upstaging us.