Soyuz 4

Soyuz 4 (Russian: Союз 4, Union 4) was launched on January 14, 1969. On board the Soyuz 7K-OK spacecraft was cosmonaut Vladimir Shatalov on his first flight. The aim of the mission was to dock with Soyuz 5, transfer two crew members from that spacecraft, and return to Earth. The previous three Soyuz flights were also dock attempts but all had failed for various reasons.

The radio call sign of the crew was Amur, while Soyuz 5 was Baikal. This referred to the trans-Siberian railway project called the Baikal-Amur Mainline, which was under construction at the time. The mission presumably served as encouragement to the workers on that project.