In Saint Petersburg, Russian scientist Alexander Stepanovich Popov demonstrates to the Russian Physical and Chemical Society his invention, the Popov lightning detector — a primitive radio receiver. In some parts of the former Soviet Union the anniversary of this day is celebrated as Radio Day.

Cheka, the first Soviet secret police, is founded.

The Soviet Union adopts the Gregorian calendar (on 1 February according to the Julian calendar).

Azerbaijan is added to the Soviet Union.

Part of Petsamo Province is ceded by the Soviet Union to Finland.

The second Peace of Riga between Poland and Soviet Union.

The Treaty of Rapallo, pursuant to which Germany and the Soviet Union re-establish diplomatic relations, is signed.

The Union of Soviet Socialist Republics is formed.

The United Kingdom recognizes the USSR.

The Soviet Union signs an agreement with the Peking government, referring to Outer Mongolia as an "integral part of the Republic of China", whose "sovereignty" therein the Soviet Union promises to respect.

The Soviet Union signs an agreement with the Peking government, referring to Outer Mongolia as an "integral part of the Republic of China", whose "sovereignty" therein the Soviet Union promises to respect.

Diplomatic relations between Mexico and the Soviet Union are established.

The Georgian opposition stages the August Uprising against the Soviet Union.

The Uzbek SSR is founded in the Soviet Union.

Diplomatic relations between Japan and the Soviet Union are established.

The most famous Young Pioneer camp of the USSR, Artek, is established.

Secret agent Sidney Reilly is executed by the OGPU, the secret police of the Soviet Union.

The Treaty of Berlin is signed. Germany and the Soviet Union each pledge neutrality in the event of an attack on the other by a third party for the next five years.

Metropolitan Sergius proclaims the declaration of loyalty of the Russian Orthodox Church to the Soviet Union.

Leon Trotsky is expelled from the Soviet Communist Party, leaving Joseph Stalin in undisputed control of the Soviet Union.

The Soviet Union introduces its First Five-Year Plan.

The Soviet Union exiles Leon Trotsky.

Soviet troops attempt to cross the Amur River into Manchuria near Blagoveschensk as tensions mount between the Soviet Union and the Republic of China.

Soviet troops attempt to cross the Amur River into Manchuria near Blagoveschensk as tensions mount between the Soviet Union and the Republic of China.

''Ready for Labour and Defence of the USSR'', abbreviated as ''GTO'', is introduced in the Soviet Union.

France and the Soviet Union sign a neutrality/no attack treaty.

France and Soviet Union sign a treaty of non-aggression.

Diplomatic relations between the Soviet Union and Spain are established.

Yevgeniy Abalakov is the first man to reach the highest point in the Soviet Union, Communism Peak (now called Ismoil Somoni Peak and situated in Tajikistan) (7495 m).

United States recognizes Soviet Union.

The Candidate of Science degree is established in the USSR.

The Soviet steamship ''Cheliuskin'' sinks in the Arctic Ocean.

In the Soviet Union, Politburo member Sergei Kirov is shot dead by Leonid Nikolayev at the Communist Party headquarters in Leningrad.

Diplomatic relations between the Soviet Union and Colombia are established.

The world's first children's railway opens in Tbilisi, USSR.

''Pravda'' publishes a letter by Pavel Postyshev, who revives New Year tree tradition in the Soviet Union.

In Berlin, Germany and Japan sign the Anti-Comintern Pact, agreeing to consult on measures "to safeguard their common interests" in the case of an unprovoked attack by the Soviet Union against either nation. The pact is renewed on the same day five years later with additional signatories.

The Soviet Union adopts a new constitution and the Kirghiz Soviet Socialist Republic is established as a full Union Republic of the USSR.

The Soviet Union adopts a new constitution and the Kirghiz Soviet Socialist Republic is established as a full Union Republic of the USSR.

Great Purge: The Soviet Union under Joseph Stalin executes eight army leaders.