the border and broke all diplomatic relations with Poland. The two countries remained at the de facto state of war until the Polish ultimatum to Lithuania in 1938. Poland Poles together with Jews, made up a majority in the city of Vilnius itself. In the years 1920–1939 Poles made up 65% of the population, Jews 28%, 4% Russians, 1% Belarusians 1% Lithuanians. Most notable cases were political imprisonment of Lithuanian cultural figures in the late 1920s: Petras Kraujalis, Pranas Bieliauskas, Kristupas Čibiras, Vincas Taškūnas, Povilas Karazija, Juozas Kairiūkštis, Vytautas Kairiūkštis, Kostas Aleksa and others, political process of May 1925, where 22 Lithuanians, that were under the threat of the death penalty, but were saved by Tadeusz Wróblewski, etc. In 1936, a secret anti-Lithuanian memorandum was issued by the Polish administration, that discussed the measures of suppression of Lithuanian minority in Vilnius and the adjacent region, controlled by Poland. In spite of the unfavorable geopolitical situation (which prevented the trade with the immediate neighbors of Lithuania, Germany and Soviet Russia, life in the town flourished. A new trade fair was created in 1928, the Targi Północne. A number of new factories, including modern "Elektrit" radio factory was opened. Much of the development concentrated along the central Mickiewicz Street, where the modern Jabłkowski Brothers department store was opened, equipped with lifts and automatic doors. New radio buildings and towers were erected in 1927, including the site where noted Polish poet and Nobel Prize winner Czesław Miłosz worked. The city's university was reopened under the name Stefan Batory University, and Polish was reintroduced as the language of instruction. By 1931 the city had 195,000 inhabitants, which made it the fifth-largest city in Poland. The city became an important centre of Polish cultural and scientific life, while economically the rest of the region remained relatively backward. It was claimed that this relative underdevelopment, among other issues, was the reason for difficulties with integrating the region and the city with Lithuania when it regained Vilnius in 1939. Vilnius was also an informal capital of Yiddish at that time. The Museum of Jewish culture was founded there in 1919, and YIVO – Institute for Jewish Research, was founded there in 1924. Several important Jewish cultural institutions including theatres, newspapers and magazines, museums and schools, and Jewish PEN-Club were created before Second World War in Vilnius. Four YIVO directors emigrated to New York. World War II Lithuanian