Soviet aspirations to send humans to the Moon date back to the early 1960s when legendary Chief Designer Sergey Korolev proposed a number of projects to send Soviet cosmonauts around the Moon and back, i.e., a “circumlunar” mission.

In 1960, Korolev had also tabled plans to build a series of giant rocket boosters known as the N1 and N2. These rockets would be used for a variety of missions such as lunar and planetary exploration and military operations. In 1962, the Soviet government formally approved work on the N1. The rocket, which still did not have a single well-defined mission, was designed to lift 75 tons into orbit.

 
Cosmonaut Aleksey Leonov in training for lunar landing approaches using a specially equipped helicopter. This photo dates from around 1969.

By 1964, the tenor of the Soviet Moon plans changed significantly because of two factors. First, the National Aeronautics and Space Administration (NASA) in the United States had embarked on its Apollo program to land astronauts on the Moon before the end of the decade. By this time, simplified Apollo hardware was being tested in space, prompting the Soviets to reconsider their slow path of a simple circumlunar mission. Second, Korolev had a powerful rival within the Soviet space program, Vladimir Chelomey, who insisted on a major role in the Moon program. Rumour had it that Chelomey was favoured by then-Soviet premier Nikita Khrushchev because Khrushchev's son, an engineer, worked for Chelomey.

The Soviet military, specifically the Strategic Missile Forces, which controlled the purse strings of the space program, was reluctant to support a politically motivated project like a Moon program that had little or no military utility. Instead, the Missile Forces lobbied for massive funding to develop intercontinental ballistic missiles (ICBMs). The desire to build new ICBMs took away from money needed for a Moon mission.

Korolev, however, was a headstrong person, and invoking the threat of Apollo, managed to convince an initially reluctant Khrushchev to compete with Apollo. In August 1964, Khrushchev signed the papers approving a project known as L3 to land Soviet cosmonauts on the Moon before the Americans. The L3 spacecraft would be launched into orbit on the giant N1 rocket, which had now been redesigned to lift 95 tons into Earth orbit. Additionally, Khrushchev gave Chelomey a parallel project, known as the LK-1, to send two cosmonauts around the Moon.

Progress on both these programs was hindered by vicious political infighting between designers in the upper echelons of the Soviet space program. The most influential designer of rocket engines in the Soviet Union, Valentin Glushko, supported developing engines for the N1 using storable propellants, i.e., those that were suitable for use on ICBMs, which needed to be at a constant ready state. Korolev, on the other hand, believed that super-cooled cryogenic propellants such as liquid oxygen offered better energy characteristics, and would be the best choice for the giant N1 rocket. The two men were unable to agree on this point, and a special commission in 1962 sided with Korolev's recommendation. Because Glushko refused to build cryogenic engines, Korolev was forced to ask an aviation engine designer named Nikolay Kuznetsov to produce engines for the N1. It was a huge gamble for Korolev since Kuznetsov had almost no experience in designing rocket engines.

There was also infighting over who would have influence in the circumlunar project. After Khrushchev's overthrow in late 1964, Korolev mounted a campaign to wrest the circumlunar project from Chelomey. In October 1965, the Soviet government accepted a compromise. Chelomey's LK-1 project was cancelled. Instead, Korolev would now use a stripped down Soyuz spacecraft known as the L1 to send cosmonauts around the Moon. Chelomey's powerful Proton rocket would launch the L1 spaceship. The Soviet government set the target date of the first L1 circumlunar mission for late 1967, the 50th anniversary of the Bolshevik Revolution.

Thus, by 1965, the Soviet Moon program had split into two parallel strands: one, the N1-L3 to land cosmonauts on the Moon, and another, the L1 to send cosmonauts around the Moon.

 
Two N1 Moon rockets appear on the pads at Tyura-Tam in early July 1969. In the foreground is booster number 5L with a functional payload for a lunar-orbiting mission. In the background is the 1M1 ground test mock-up of the N1 for rehearsing parallel launch operations.

All these disagreements cost the Soviets in terms of time and money. The Soviet Moon program was also hampered by Korolev's premature death in 1966. He was succeeded by his deputy Vasily Mishin.

The N1 rocket (with the L3 spaceship complex attached) was a behemoth 345 feet (105 meters) long and weighing about 2,750 tons. The first stage had 30 engines, the second stage had eight, and the third had four. All of these engines were powered by liquid oxygen and kerosene and designed by Kuznetsov's inexperienced organization. Because of lack of time and money, Soviet designers decided to skip full-scale testing of the first stage on the ground. This decision later proved to be a fatal one since ground-testing of the first stage might have eliminated many problems that arose during actual launches.

The L3 complex comprised a translunar boost stage, an upper stage to brake into lunar orbit, a lunar orbiter, and a lunar lander. Unlike the American Apollo spacecraft that carried three people, the Soviet L3 spacecraft would carry two cosmonauts, one to land on the Moon and one to circle the Moon.

In the late 1960s, the Soviets finally launched a series of L1 spacecraft to the Moon that were publicly known as Zond (the Russian word for “probe”). None of these carried crews. Despite a series of crushing failures, Mishin continued to persevere and planned to send the first cosmonauts around the Moon in December 1968, a few days before NASA's planned Apollo 8 mission that would carry three astronauts into lunar orbit. After a last test spacecraft, Zond 6, failed to land safely, Mishin postponed a piloted Zond mission. In the end, Apollo 8 flew to the Moon in late December 1968 and claimed one of the great firsts of the space era. After the resounding success of the Americans, the Soviet government decided to cancel the L1 project in 1970.

The N1-L3 landing project did not fare any better. After years of delay, the first N1 rocket was launched in February 1969. Because of a fire at the bottom of the first stage, all engines shut down 70 seconds after launch, and the booster crashed without ever making it into orbit. During the second launch in July 1969, just two weeks before the Apollo 11 mission, the N1 rocket failed to rise beyond 656 feet (200 meters) above the pad. Because of an explosion of an engine, the booster collapsed back onto the launch pad in a massive explosion that destroyed millions of dollars of equipment. The third N1 launch in June 1971 also failed when the booster's first engines shut down about 50 second after launch. During a final launch in November 1972, just before second stage ignition, there was a failure that caused the rocket to explode in flight. Most of these failures could have been avoided had the rocket's first stage been tested on the ground.

Despite the failures, Mishin continued to work doggedly on the Moon program. By 1974, he had begun work on a more advanced project known as L3M to land large modules on the Moon for long-term exploration. Most engineers were confident that the fifth and sixth N1 launches, scheduled for 1974, would be successful since they would use more advanced and reliable engines.

The Soviet government did not share this enthusiasm. In May 1974, the government cancelled the project despite protests from thousands of engineers. They did not see any use in spending millions on a Moon program when the Americans had already reached the Moon five years before. The government ordered the destruction of all remaining equipment related to the N1. Korolev's old rival Glushko, who had viciously opposed the N1 program, was now put in charge of the Soviet human space program. Mishin was fired and blamed for the failure of the project. He was ordered to remain silent and his name was never mentioned in any Soviet space history book until 1989, after Glushko's death.