Timeline of The Great Purge

1937

January 6: Soviet Census (1937). The population of the Soviet Union was found to be much less than expected. The Census was classified and its authors imprisoned (September 1937).
January 8: A letter from the Narkom of Justice and the Procurator-General ordered military tribunals to hear all cases where military, diplomatic or state secrets might be involved in closed hearings without legal representation of the accused.
January 9: NKVD Directive on implementation of the December 17 decree of Sovnarkom. The directive exiled from Azerbaijan 2,500 Iranian nationals and 700 families of counterrevolutionary elements (former mullahs, kulaks, persons previously sentenced).
January 23 - January 30: Trial of the "Parallel Trotskyist-Zinovievist Center". Among those sentenced to death were Pyatakov, Radek, Grigory Sokolnikov, and Nikolai Muralov.
January 27: Yezhov received the rank of General Secretary of State Security (General'nij Sekretar' Gosbezopasnosti). Simultaneously Yagoda is retired from that rank.
February 18: Death of Sergo Ordzhonikidze. The death was most probably a suicide related to the upcoming purge.
February 23 - March 5: Plenum of the Central Committee of the CPSU. Most of the Plenum was devoted to the upcoming mass repressions and the case against Bukharin and Rykov. On February 27, both were excluded from the Communist Party and arrested. Reports by Vyacheslav Molotov and Lazar Kaganovich were devoted to Lessons of the sabotage and spying of Japanese-German-Troskyist agents in industry and in transport. The report of Yezhov was devoted to Purging the NKVD. The long report by Stalin was named Deficiencies in the party work and measures for liquidation of Trotskyists and other turncoats (О недостатках партийной работы и мерах ликвидации троцкистских и иных двурушников). He stated that the liquidation of the enemies should be the priority for all the Party members, and proposed changing from "the old methods, the methods of discussions to the new methods of uprooting and liquidation". In total 73 people addressed the Plenum. 56 of them were executed in 1937-1940; two committed suicide; 15 including Stalin, Molotov, and Kaganovich themselves survived beyond 1940.
February 27: Yezhov presented to the Politburo the List of persons to be judged by the Military Collegium of the Supreme Court. 475 people were recommended for execution. In 1937 more than 40,000 people were recommended for execution by similar Politburo lists.
March 11: NKVD directive on the "Trotskyist-Japanese plot in the oil industry".
March 15: NKVD directive on strengthening the regime for the political prisoners.
March 17: Adoption opf USSR law banning peasants from leaving their collective farms. The official end for the freedom of movement.
March 23: NKVD directive indefinitely prolonging all sentences of political exile.
March 27: Letter of the NKVD on Intensifying work on churches and sects.
March 29: The Politburo ordered the Red Army to dismiss all officers excluded from the Party.
April 2: NKVD letter on stepping up the work on German agents in the ethnic German population.
April 3: NKVD letter on stepping up the purge of enemy agents from the Military-Chemical industry.
April 8: Increased powers given to the Extrajudicial Special Commission of the NKVD (Osobye Soveschaniye), giving them power to imprison up to 8 years without trial (it was 5 years of exile before).
April 15: The head of the State Security department (GUGB) of the NKVD, Yakov Agranov, was replaced by Mikhail Frinovsky.
April 21: Order of the NKVD and Procurator-General banning shortening prison sentences for the political prisoners.
April 29: Order of the NKVD for immediate liquidation of the "menshevik underground".
May 7: Order of the NKVD for stepping up the agenturas work among athletes.
May 14 - May 29: Arrests of military leaders, under the "Case of Trotskyist Anti-Soviet Military Organization".
May 23: Politburo decree exiling from Moscow, Leningrad and Kiev all persons ever excluded from the Communist Party for the relations with opposition and all family members of persons imprisoned for more than five years.
June 8: Order of the NKVD on Anti-Soviet Turkic-Tatarian Nationalist Organizations. The order states that terrorist nationalists took the leading positions in Azerbaijan, Crimea, Tatarstan, Uzbekistan, Tajikistan, and Kazakhstan, and requires a step-up of arrests there
June 11: Case of Trotskyist Anti-Soviet Military Organization is heard by the Supreme Court. Eight military leaders: Mikhail Tukhachevsky, Iona Yakir, Ieronim Uborevich, Vitaly Markovich Primakov, Vitovt Putna, Avgust Kork, Robert Eideman, and Boris Feldman are sentenced to death and executed the following night
June 15: Operation removing from Moscow, Leningrad, Kiev, Rostov-on-Don, Taganrog, and Sochi all persons excluded from the Communist Party and the family members of prison inmates. (See May 23.)
June 21: Order of the Narkomat of Defence and NKVD pardoning those people who voluntarily informed the NKVD of their Anti-Soviet activities.
June 23 - June 29: The Plenum of the Central Committee heard the report of Yezhov about the Plot propagated in all structures of the Party and State.
June 28: The Politburo considered the letter from Robert Eikhe, The First Secretary of the Western Siberian committee of the Communist Party on the Anti-Soviet organization among exiled kulaks. The Politburo decided to create the first NKVD troika for the suppression of kulaks in Western Siberia. The NKVD troika was the first extrajudicial organ having power to issue death sentences.
July 2: The Politburo adopted the On Anti-Soviet elements resolution. The resolution gave five days to each Soviet republic, krai, and oblast to create an NKVD troika and present the numbers of former kulaks needed to be sentenced to death.
July 5: Politburo resolution On Family Members of the Traitors ordered that all wives of "Trotskyist and right spies" be sent to labor camps for at least five to eight years, while their children should be placed in the "special orphanages".
July 7: Letter from the Procurator-General decreed that "all hooliganism" having contra-revolutionary or chauvinistic motives was classified as a political crime (58-10 "Anti-Soviet propaganda" or 59-7 "Propaganda of National Hatred").
July 14: Opening of the Moscow Canal, built by GULAG inmates. Before the opening of the canal, 218 prisoners were executed for allegedly plotting to assassinate Stalin during the ceremomy.
July 20: Resolution of the Politburo ordering NKVD to arrest all ethnic Germans working in defense industries.
July 20: NKVD order requiring an account of all ethnic Poles working on railroads or in defense industries, whether there was any compromat or not. Beginning of preparations for the "Polish operation".
July 24: Instruction of the NKVD For the prevention of bacteriological diversions": an order to arrest all people with foreign connections and "anti-Soviet elements" working in water supply or in bacteriological laboratories.
July 25: NKVD order 00439 On repressions of Germans suspected of spying against the USSR started the "German operation". In 1937-1938 55,005 people were sentenced due to the "German operations". Among them 41,898 people were executed.
July 27: NKVD Directive On purging the Military Intelligence Department of the Red Army
July 29: NKVD Directive On purging railroad workers of socially harmful elements
July 31: NKVD operative order 00447 «Об операции по репрессированию бывших кулаков, уголовников и других антисоветских элементов» (The operation for repression of former kulaks, criminals and other anti-Soviet elements) is approved by the Politburo. Originally the operation was planned for four months; the plan was for 75,950 people to be executed and an additional 193,000 to be sent to the GULAG. The operation was extended multiple times. Altogether, through the summer of 1938, at least 818,000 people were arrested and not less than 436,000 were executed.
Second half of July: Instruction of the Politburo allowing unlimited use of torture. The actual instruction has not been found yet, but its content has been reconstructed from later instructions limiting the use of torture.
August 1: Resolution of the Sovnarkom and Central Committee On fighting the sabotage in grain appropriation.
August 5: Start of the Kulak operation: mass arrests of those planned to be executed (so called 1st category).
August 5: Instruction of the NKVD On implementation of Order 00447 in labor camps. Each camp received orders for the number of prisoners to be executed. The death sentences were to be proposed by the camp administrations and confirmed by NKVD troikas.
August 7: A letter from Vyshinsky stated that executions and imprisonments under Order 00447 do not require confirmation from any judicial body.
August 11: NKVD operative order 00485 «О ликвидации польских диверсионно-шпионских групп и организаций ПОВ » (On liquidation of Polish diversion-spying groups and elements of Polish Military Organization). The following groups were supposed to be repressed: former POWs from Poland, emigrants from Poland, and members of the Polish Socialist Party and other Polish political parties. Also the order indefinitely prolonged the prison sentences of everybody suspected of being a Polish spy. The order created a new extrajudicial organ: NKVD dvoyka consisting of two people: a representative of the NKVD and a representative of the Procurator-General. It also created a new process for sentencing: "album sentencing". The sentencing was done by correspondence using lists of accused bound for easy of handling into special "albums" (hence the name). In 1937-1938, 139,815 people were sentenced in the course of the "Polish operation"; among them 111,071 people were executed.
August 15: NKVD operative order 00486 On repression of the family members of traitors, Trotskyists, and other citizens sentenced by the Military Collegium and the Special Commission. The order required wives and children older than 15 years old to be sent to the GULAG for 5 to 8 years; children younger than 15 were put in "special orphanages". There were 19,000 wives were arrested and 25,000 children were removed.
August 16: Creation of seven new "Forest GULAGs" for the people arrested under Order 00447 (second category).
August 17: Directive of the NKVD On extending NKVD operative order 00485 to Romanian spies. 8,292 were arrested; among them 5,439 were executed.
August 21: Resolution of the Central Committee and Sovnarkom On transfer of Koreans from the Far East. The resolution ordered exile of all ethnic Koreans from the Russian Far East to Central Asia.
August 22: Instruction of the NKVD On Foreigners. This instruction stated that almost all of the foreign nationals are spies, so no residence permits are to be extended for the nationals of Germany, Poland and Japan.
September 14: Changes in the Process Code (Protsesual'nikj kodeks), banning appeals of the sentences under articles 58-7 (sabotage) and 58-9 (diversion). All persons sentenced under these articles should be executed within one day after the court sentence.
September 20: NKVD operative order 00593 «О мероприятиях в связи с террористической, диверсионной и шпионской деятельностью японской агентуры из так называемых харбинцев» (On measures connected with terrorism, diversions and spying by Japanese agents among so-called Harbinians). The order stated the need to arrest people who had ever worked in Chinese territory. 46,317 were arrested, among them 30,992 were executed.
October 2: Extension of the maximum prison sentence from 10 years to 25 years.
October 2: Resolution of the Sovnarkom and Central Committee On fighting sabotage in animal breeding
October 8: Order of Procurator General Vyshinsky that courts should classify negative opinions on Soviet and Party leaders as 58-8 (aid to terrorists) rather than 58-10 (contra-revolutionary agitation).
October 11: NKVD resolution on transferring Azerbaijan Kurds to Central Asia (486 families exiled).
October 12: Yezhov became a candidate for Politburo membership.
October 23: NKVD order 00693 «Об операции по репрессированию перебежчиков – нарушителей госграницы СССР» stating that anybody illegally crossing borders of Soviet Union should be arrested without regard to their motives (e.g. refugee from Nazi Germany).
October 28: NKVD order 00698 «О пресечении к.-р. шпионской, террористической, диверсионной деятельности личным составом посольств и консульств Германии, Японии, Италии и Польши». The order decreed that every Soviet citizen who had ever worked for the embassies and consulates of Germany, Japan, Italy or Poland was to be arrested.
October 12-November 5: NKVD instruction ordering Operative defeat of Anti-Soviet Church and sectarian actives.
November 3: NKVD instruction for stepping up the mass operations (against kulaks, ethnic people and family members of traitors).
November 4: NKVD instruction for stepping up the work among Gypsies.
November 30: NKVD instruction for the Mass operation against Latvian spies: 21,300 people were arrested; among them 16,575 were executed.
December 11: NKVD instruction (directive No 50215) for the Mass operation against Greeks: 12,557 people arrested; among them 10,545 were executed.
December 14: The November 30th operation against Latvians was extended to Estonians, Finns, and Bulgarians. 9,735 Estonians were arrested; among them 7,998 were executed. 11,066 Finns were arrested; among them 9,078 were executed.
December 17: Instruction of the NKVD for execution of all GULAG escapees.
December 22: Instruction of the NKVD for repression of the ethnic Chinese, ordering arrests "for every provocative action or terrorist intentions."

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Timeline of The Great Purge - 1937