However, from the late 19th century and especially with the economic boom of the 1950s–1960s, Northern Italy and especially the cities of Turin, Genoa, and Milan was the most important region in the Italian industrialization and sharpened its status of richest and most industrialized part of Italy. Between 1943 and 1945, during the Second World War, Northern Italy was part of the Fascist Italian Social Republic and the main theatre of the anti-fascist partisan activity. Between April 19 and 25, 1945 the cities of Northern Italy began an insurrection against Fascist and Nazist forces that led to the liberation of Northern Italy by Allied forces Economic differences between Northern Italy and the rest of the country, as well as the short history of Italy as a single nation, led in the 1990s to the emergence of Padanian nationalism, as Lega Nord promoted either secession or larger autonomy for Padania, the name chosen to represent Northern Italy.