The growth of the Russian population was due to several factors. The Civil war and the establishment of Soviet power in Russia caused a flow of refugees and emigrants to many countries, Latvia included. After the Battle of Daugavpils in 1920 Poles relinquished control of Dvinsk with the majority of the Russian population to the Latvians. According to the Peace Treaty between the Latvian Republic and Soviet Russia, some lands of the Pskov province with a large number of Russians passed on to Latvia. But the main cause of the Russian population growth was their high natural birth rate. For example, in 1929 the natural increment of Russians was 2,800, while the natural increment of Latvians, whose total number in that same year was nine times as big as that of Russians, made up only 3,700.