42,000 Latvians were hauled off in cattle trucks on March 25, 1949 alone and the date is now designated as Communist Genocide Memorial Day, with flowers laid at many of the rail points used for the deportations.
Similar atrocities against the local populations were also committed in Estonia and Lithuania.
Two major waves of mass deportations were carried out in Latvia: during the first Soviet occupation in 1941, and in 1949, during the second occupation, though smaller-scale deportations to the Gulag took place at other times as well.
As well as being crimes against humanity, the deportations deprived Latvia of its national elites, and created shortages in the labor force, which were made up by immigrants from other parts of the Soviet Union as part of a wider program of Russification.
The deportations also created an entire generation of Latvians born in Siberia, who today are known as the 'Children of Siberia'.
"Though not outright genocide, the deportations created conditions that set Latvia and its people on a course of losing its cultural heritage and eventually its national identity as well," says an official account of the deportations by the Museum of the Occupation of Latvia. A full account of the Soviet Union's appalling actions in this regard is available here.
Many officials and members of the public provided reminders of the day's significance on social media, including Latvia's ambassador to the Russian Federation, Māris Riekstiņš, on the even of a possible sequence of diplomatic expulsions between Moscow and the West.
OTD 1949 secret operation “Priboi” started. Within few days more than 90000 people from occupied Baltic States had been sent to remote places in Siberia - a crime by Stalin and his regime - not to be forgotten. We commemorate the victims of #deportations pic.twitter.com/HFHETIEaI2— Māris Riekstiņš (@Riekstins__M) March 25, 2018
President Raimonds Vējonis provided a March 25 thought, saying: "No-one has the power to turn back time and change history. But we can always learn from those who were part of it how valuable our freedom is and what it means never to give up, whatever difficulties are placed in our way."
Pieminot komunistiskā genocīda upurus. pic.twitter.com/mYwKhuDlpj— Valsts prezidents (@Rigas_pils) March 25, 2018