"On August 5, 1940, the independent country of Latvia was forcibly incorporated into the Soviet Union. Thousands of Latvians were arrested for having anti-Soviet views, taking part in resistance movements, being farmers, belonging to political parties, or refusing to join a collective farm. Many were deported to Siberia.
People who were in prisons, concentration camps, or settlements in Siberia wrote letters to friends and relatives on birch bark, which was often the only available material at places of deportation. This was particularly the case during World War II, when paper was very scarce. Only 19 such letters, dating from 1941 to 1956, survive in Latvian museums. They are important documents for the history of Latvia and of the Soviet era and a vivid record of the effects of mass repression on individual lives.”
From the Siberian Letters on Birch Bark collection at the National Library of Latvia