From February 1920, he served as a representative of Kazrevkom in the management department of the Orenburg Governorate Executive Committee "for the organization of rear militia".

His term began at the time of the first Soviet ambassador to Mexico, Stanislav Pestkovsky, who served in the office until 1926 and would later be among those who perished in Stalin's Great Purge of 1937.

In 1925, Gaikis met with Vladimir Mayakovsky on the latter's arrival to Mexico, and helped the poet obtain a visa to the United States.

Having allegedly supported back in 1923, during Lenin's terminal illness, The Declaration of 46, which called for greater party democracy and preceded the formation of the Trotsky-led Left Opposition,[6] Gaikis was now starved, tortured, interrogated and prosecuted, like many others, under the charge of Trotskyism.

[7] The order was formally affirmed by the Military College of the Supreme Court of the Soviet Union, which sentenced him to death "for betrayal of the Fatherland and belonging to a counter-revolutionary terrorist organization".

After the purge of Rosenberg and Gaikis, no official ambassador was appointed again, and the embassy was headed by the chargé d'affaires, until the defeat of the Spanish Revolution with the fascist victory of Franco's forces in 1939, which saw the break of all diplomatic relations.

The chargé d'affaires, Sergey Marchenko, was arrested after returning to Russia in 1939, on charges of participation in a counter-revolutionary terrorist organization, and was executed in July 1941.

Vladimir Antonov-Ovseenko, the Soviet Consul General in Barcelona, a former Left Opposition member, was recalled to Moscow in August 1937 and within months was arrested and shot.

She was immediately expelled from the Communist Party of the Soviet Union and in 1941 was arrested by a law that held responsible the closest relatives of incriminated people.

In 1945, at the end of the Second World War, she was released as part of a deal acquired by the Union of Polish Patriots and was sent to the wrecked Warsaw.

After the death of Stalin, as part of the so-called de-Stalinization, Leon Gaikis was posthumously rehabilitated, on 17 December 1955, by the Military College of the Supreme Court of the Soviet Union.