Later, Chelomei also proposed a Moon landing program with a super-heavy UR-700 rocket, an LK-700 lunar lander, and an LK-3 spacecraft. R-56 The R-56 which was developed between April 1962 and June 1964 was considered for involvement with the lunar program. Reaction to Apollo In the early stage of the Soviet and US crewed lunar program, Kennedy proposed before the United Nations a joint Moon program, a proposal which was considered by Khrushchev. The proposal disappeared though with Kennedy's assassination two months later, but nevertheless foreshadowed the Apollo-Soyuz mission, which enabled subsequently the Shuttle-Mir program and the ISS. The Soviet government issued a response to the American Apollo challenge after three years. According to the first government decree about the Soviet crewed Moon programs (Decree 655-268, ' On Work on the Exploration of the Moon and Mastery of Space '), adopted in August 1964, Chelomei was instructed to develop a Moon flyby program with a projected first flight by the end of 1966, and Korolev was instructed to develop the Moon landing program with a first flight by the end of 1967. Following the change from Nikita Khrushchev to Leonid Brezhnev in 1964, the Soviet government in September 1965 assigned the flyby program to Korolev, who redesigned the cislunar mission to use his own Soyuz 7K-L1 spacecraft and Chelomei's Proton rocket. Korolev organized full-scale development of both programs, but died after surgery in January 1966. According to a government decree of February 1967, the first crewed flyby was scheduled for mid-1967, and the first crewed landing for the end of 1968. Moon flyby UR-500K(Proton)/L1(Zond) program Launched by a 3-staged Proton rocket, the L1 (Zond) was a spacecraft from the Soyuz family and consisted of two or three modified modules of the main craft Soyuz 7K-OK with a total weight of 5.5 tons. The Apollo orbital spacecraft (command ship) for the lunar flyby also had two modules (command and service) but was five times heavier, carried a crew of three and entered lunar orbit, whereas the L1 (Zond) performed a flight around the Moon and came back on a return trajectory. In September 1968 Zond 5 carried the first Earth lifeforms, including two tortoises, to travel around the Moon and return safely. Planned for 8 December 1968 for priority over the US, a first crewed mission of the L1 (Zond) was canceled due to the insufficient readiness of the capsule and