Vladimir Shatalov would become the Soviet Union’s 13th space traveler, his home telephone number ended in “13” and the launch itself was set for 13:00 hours Moscow Time, on January 13th, 1969.
The objectives of the Soyuz 4 & 5 mission were to dock two manned Soyuz 7K-0Ks, transfer two Cosmonauts from Soyuz 5 to Soyuz 4 by means of a space walk, and then safely return both crews to earth.
Trouble began on the sixth day of the flight, November 17. The capsule developed an atmospheric leak, the pressure first dropping from 760 to 380 mm of Mercury. With the drop in cabin pressure all the animal test subjects died. It would have killed any Cosmonaut not wearing a spacesuit.
The soviets showed some confidence in their spacecraft by launching the unmanned Soyuz 2 first, but showed some caution by not sending a cosmonaut in Soyuz 2.