On 25 September, Moscow demanded that Estonia sign a Soviet–Estonian Mutual Assistance Treaty to allow the USSR to establish military bases and station troops on its soil.

Moscow presented ultimatums, demanding new concessions, including the replacement of governments with new ones, "determined to fulfill the treaties of friendship sincerely" and allowing an unlimited number of troops to enter the three countries.

[12] The Ulmanis government decided that, given the conditions of international isolation and the overwhelming Soviet force both on the borders and inside the country, it was better to avoid bloodshed and an unwinnable war.

[20] The newly elected People's Parliament convened on 21 July and announced both the creation of the Latvian SSR and the request of admission into the Soviet Union.

[citation needed] Therefore, the history of Soviet Latvia can broadly be divided into the periods of rule by the First Secretaries: Jānis Kalnbērziņš, Arvīds Pelše, Augusts Voss, and Boris Pugo.

[21] The small size of land plots and imposition of the production quotas and high taxes meant that very soon independent farmers would go bankrupt and had to establish collective farms.

[citation needed] Initially, they were limited to the most prominent political and military leaders like President Kārlis Ulmanis, War Minister Jānis Balodis, and Army Chief Krišjānis Berķis, who were arrested in July 1940.

[citation needed] In early 1941, the Soviet central government planned the mass deportation of anti-Soviet elements from the occupied Baltic states of Lithuania, Latvia, and Estonia.

During the night of 13 to 14 June 1941, 15,424 inhabitants of Latvia — including 1,771 Jews and 742 ethnic Russians — were deported to camps and special settlements, most of which were in Siberia.

[citation needed] The start of Operation Barbarossa cut short immediate plans to deport several hundred thousand more people.

[citation needed] Immediately after the installment of Nazi German authority, a process of eliminating the Jewish and Gypsy populations began, with many killings taking place in Rumbula.

[citation needed] Forest brothers consisted not only of the former Legionnaires or German supporters but men who were trying to avoid Soviet conscription, dispossessed farmers, and even priests and school pupils who wrote and distributed patriotic leaflets and provided shelter to partisans.

[citation needed] On 25 March 1949, 43,000 primarily rural residents ("kulaks") were deported to Siberia and northern Kazakhstan in Operation Priboi, which was implemented in all three Baltic States and was approved in Moscow on 29 January 1949.

[citation needed][27] In the post-war period, Latvia was forced to adopt Soviet farming methods, and the economic infrastructure developed in the 1920s and 1930s was eradicated.

The lack of politically reliable local cadres meant the Soviets increasingly placed Russians in Party and government leadership positions.

[21] Hundreds of thousands of Russians were moved to Latvia to replace the lost population (due to war casualties, refugees to the West, and deportees to the East) and to implement a heavy industrialization program.

In addition, the Russian people's leading and progressive role throughout Latvian history was heavily emphasized in school books, arts, and literature.

The remaining poets, writers, and painters had to follow the strict canons of socialist realism and live in constant fear of being accused of some ideological mistake that could lead to banning from publication or even arrest.

By this time many locally-born communists had achieved positions of power and began advocating a program that centered on ending the inflow of Russian-speaking immigrants, ending the growth of heavy industry, and creating light industries better suited for local needs, increasing the role and power of the locally born communists, enforcing the Latvian language as the state language.

The speed of Russification was also influenced by the fact that Riga was the HQ of the Baltic Military District, with active and retired Soviet officers moving there.

To improve rural living standards, a mass campaign was started to liquidate individual family farms and to move people into smaller agricultural towns where they were given apartments.

[citation needed] In the second half of the 1980s, Soviet leader Mikhail Gorbachev began the introduction of the political and economic reforms of glasnost and Perestroika.

It also argued that the 1940 resolution acceding to the Soviet Union was illegal since the 1922 Latvian constitution stipulated that any major change in the state order had to be submitted to a referendum.

On these bases, the Supreme Council argued that the Republic of Latvia, as proclaimed in 1918, still legally existed even though its sovereignty had been de facto lost in 1940.

[34] Latvia took the position that it did not need to follow the process of secession delineated in the Soviet constitution, arguing that since the annexation was illegal and unconstitutional, it was merely reasserting independence that still existed under international law.

In January 1991, Soviet political and military forces unsuccessfully tried to overthrow the Republic of Latvia authorities by occupying the central publishing house in Riga and establishing a Committee of National Salvation to usurp governmental functions.

The Republic of Latvia declared the end of the transitional period and restored complete independence on 21 August 1991 in the aftermath of the failed Soviet coup attempt.

Vast numbers of people were needed for the new factories, and they were purposefully sent there from different parts of Russia, thus creating a situation wherein bigger towns became increasingly Russified until the 1980s.

Courland's entire Baltic Sea coast became a Soviet border area with limited freedom of movement for the local inhabitants and closed to outsiders.

The Pacts of Mutual Assistance were then signed[51] which allowed the USSR to station a limited number of Red Army units in the Baltic countries.