The orbital spaceflight consisted of a single orbit around Earth which skimmed the upper atmosphere at 169 kilometers (91 nautical miles) at its lowest point. The flight took 108 minutes from launch to landing. Gagarin parachuted to the ground separately from his capsule after ejecting at 7 km (23,000 ft) altitude.
The Space Race between the Soviet Union and the United States, the two Cold War superpowers, began just before the Soviet Union launched the world's first artificial satellite, Sputnik 1, in 1957. Both countries wanted to develop spaceflight technology quickly, particularly by launching the first successful human spaceflight. The Soviet Union secretly pursued the Vostok programme in competition with the United States Project Mercury. Vostok launched several precursor unmanned missions between May 1960 and March 1961, to test and develop the Vostok rocket family and space capsule. These missions had varied degrees of success, but the final two—Korabl-Sputnik 4 and Korabl-Sputnik 5—were complete successes, allowing the first manned flight.
The Vostok 1 capsule was designed to carry a single cosmonaut. Yuri Gagarin, 27, was chosen as the prime pilot of Vostok 1, with Gherman Titov and Grigori Nelyubov as backups. These assignments were formally made on April 8, four days before the mission, but Gagarin had been a favourite among the cosmonaut candidates for at least several months.:262,272
The final decision of who would fly the mission relied heavily on the opinion of the head of cosmonaut training, Nikolai Kamanin. In an April 5 diary entry, Kamanin wrote that he was still undecided between Gagarin and Titov. "The only thing that keeps me from picking is the need to have the stronger person for the one day flight." Kamanin was referring to the second mission, Vostok 2, compared to the relatively short single-orbit mission of Vostok 1. When Gagarin and Titov were informed of the decision during a meeting on April 9, Gagarin was very happy, and Titov was disappointed. On April 10, this meeting was reenacted in front of television cameras, so there would be official footage of the event. This included an acceptance speech by Gagarin. As an indication of the level of secrecy involved, one of the other cosmonaut candidates, Alexei Leonov, later recalled that he did not know who was chosen for the mission until after the spaceflight had begun.
Gagarin was examined by a team of doctors prior to his flight. One doctor gave her recollection of the events in an interview with Russia Today in April 2011: "Gagarin looked more pale than usual. He was unsociable and quiet, which was not like him at all. He would answer by nodding or a short 'yes' to all questions. Sometimes he would start humming some tunes. This was a different Gagarin. We geared him up, and hugged. And I said, 'Yuri, everything will be fine.' And he nodded back."