In 1918, the town first became part of the State of Slovenes, Croats and Serbs, then part of the Kingdom of Serbia and finally part of the Kingdom of Serbs, Croats and Slovenes. From 1918 to 1922, Šid was part of the Syrmia county, from 1922 to 1929 part of the Syrmia oblast, from 1929 to 1931 part of the Drina Banovina, from 1931 to 1939 part of the Danube Banovina, and from 1939 to 1941 part of the Banovina of Croatia. During World War II, from 1941 to 1944, the town was occupied by Axis troops and was included into the Pavelić's Independent State of Croatia. The fascist Ustashe regime systematically murdered Serbs (as part of the Genocide of the Serbs), Jews (The Holocaust), Roma (The Porajmos), and some political dissidents. On August 1942, following the joint military anti-partisan operation in the Syrmia by the Ustashe and German Wehrmacht, it turned into a massacre by the Ustasha militia that left up to 7,000 Serbs dead. Among those killed was the prominent painter Sava Šumanović, who was arrested along with 150 residents of Šid. In 1944, Šid was liberated by Yugoslav Partisans and until April 1945, a number of battles of the Syrmian Front campaign were fought near the town. The Yugoslav Partisans mined the local Catholic church during the offensive in late 1944. Since 1944, the town is part of Vojvodina, which (from 1945) was an autonomous province of Serbia and Yugoslavia.