Latvia states of Northern and Eastern Europe were divided into German and Soviet "spheres of influence". In the north, Latvia, Finland and Estonia were assigned to the Soviet sphere. A week later, on 1 September 1939, Germany and on 17 September, the Soviet Union invaded Poland. After the conclusion of the Molotov-Ribbentrop Pact, most of the Baltic Germans left Latvia by agreement between Ulmanis' government and Nazi Germany under the Heim ins Reich programme. In total 50,000 Baltic Germans left by the deadline of December 1939, with 1,600 remaining to conclude business and 13,000 choosing to remain in Latvia. Most of
Postage stamps and postal history of Latvia Postal Service routes in Finland. In 1685 the Duke of Courland Friedrich Casimir initiated his own postal service and asked the Swedish authorities to cease their postal operations within his territory, but King Charles XI of Sweden ignored his request and stood for his rights in Courland. On 5 July 1710, Russian troops under the command of Tsar Peter I of Russia took over Riga and made it a part of the Russian Empire. During World War I, Latvia was occupied by Germany, and used German stamps overprinted by the Ober Ost. In 1919, German stamps were handstamped "LIBAU", but