In 1930, Šeinbergas graduated from the clinical medicine faculty of the prestigious University of Pisa in Italy. After the 4th Chess Olympiad in 1931, he stopped playing in chess tournaments. During the Spanish Civil War, Šeinbergas joined the International Brigades and from 1937 to 1939 fought in Spain. After the disintegration of the Republican army at the beginning of 1939, Šeinbergas was interned in camps for defeated Spanish Republicans in France. From the camp he returned to Kaunas, where he married Fania Katz. The couple had two sons: Modesto (1940) and Isai (1946).