During the First Balkan War the city was ceded to Greece by the Turks (1913), according to the terms of the Treaty of Bucharest. In 1915, during the First World War, it was the headquarters of the allied forces in the east from 1915-1918; Venizelos set up his provisional government of the Greek National Defense there as well.
In 1923, huge numbers of Greek refugees from Asia Minor flooded into shanty towns after the 'catastrophe' of 1922 and the 'population exchange' (dictated by the Treaty of Lausanne) of Christian and Muslim minorities between the new Turkish nation and Greece. Thessaloniki Archeology Museum ancient greaves and head and butt from pike used in phalanx below right.
Before 1923, Orthodox Christians were in the minority, with Ottoman Muslims, Slavs (who called the city 'Solun'), Albanians, Armenians, and the aforementioned huge Jewish community. Many Jews migrated to Palestine, west Europe and the United States following World War I. During World War II, in April of 1941, Hitler's army occupied the city, and during the spring and summer of 1944, 68,000 Jews were taken to Poland to their deaths (85% of a population of 80,000 (again nearly half of the population of Thessaloniki). Their huge cemeteries were also desecrated. Later, the new university and extended trade-fair grounds were built on top of them. Only in 2001 was a Jewish museum opened, as well as a memorial to those murdered by the Nazis.