When we left the Soviet Union they had somewhat successfully landed a probe on Venus and they had completed the automatic docking of two Soyuz 7K-OK spacecrafts. However they did not reach their goal of a circumlunar flight in time for the 50th anniversary of the glorious revolution.
The success of Apollo 4 gave good reason to believe that the Saturn V could be trusted to propel men into space. But NASA pushed on with its plans for a second unmanned booster flight, primarily to give the Pad 39 launch team another rehearsal before sending men into deep space on the Saturn V. The mission was called Apollo 6…
“The fire-in-the-hole abort was the most critical test of the mission and one we had to accomplish successfully prior to a manned mission.” Gene Kranz – Flight Director Apollo 5
“…our building’s shaking here. Our building’s shaking! Oh it’s terrific, the building’s shaking! This big blast window is shaking! We’re holding it with our hands! Look at that rocket go into the clouds at 3000 feet!…you can see it…you can see it…oh the roar is terrific!…” Walter Cronkite – Apollo 4 launch.